1 Surface Cladding System This application is a divisional of Australian Patent Application No. 2009202866, the entire contents of which are incorporated herein by 5 reference. Field of the Invention This invention relates to a surface cladding system having at least one line of at least two profiled roof sheets having overlapping ends and a sealing device 10 for use in sealing between overlapping profiled sheets such as roofing sheets. Background of the Invention The sealing device has particular use in joining profiled steel roofing sheets of a long span roof. The term "long span" refers to an industrial roof that may, for 15 example, be up to 80 metres long and have a fall to enable rainwater run-off which can be as low as 10. The roofing sheets are held in place by being engaged with roofing clips mounted on a supporting roof frame over which the sheets are installed. The engagement is to be such as to allow for thermal expansion of the sheets relative to the roof frame and clips. In many systems, 20 the sheets are pushed onto the clips so as to secure a head portion of each clip above a re-entrant surface or shoulder within a rib defined by the profiled sheet. The length of roofing sheets that cover a long span can be of a relatively short, 25 transportable length, such as from 12 to 20 metres. Alternatively, the sheets can be of a relatively long continuous length of up to about 80 metres if the sheets are manufactured on site. A waterproof step joint is necessary where shorter length sheets join, but the need for such intermediate joints is avoided by using such long continuous length sheets. However, use of the long 30 continuous lengths incurs the costs of transporting a sheet roll former to manufacture the sheet on site and of the necessary handling equipment for moving the long continuous sheet onto a roof frame and into place. Those costs are high, and can be prohibitive for some roofing requirements. 857307 speci (clean) 10 July 09 2 As intimated, using short, transportable sheets necessitates a waterproof step joint where the ends of longitudinally successive sheets overlap. That is, a seal is required where the lower end of one sheet overlaps with the upper end 5 of another sheet below the one sheet. Also, there typically needs to be two purlins below and supporting each step joint. The height of a typical step joint is visually significant as it can be as great as about 100mm and, hence, it can be aesthetically undesirable. The step, in addition to providing a waterproof joint, is to function as an expansion joint. That is, the joint is to allow for 10 thermal expansion and contraction of the sheets caused by ambient temperature cycles. Summary of the Invention The present invention provides a surface cladding system having at least one 15 line of at least two profiled roof sheets having overlapping ends, each profiled roof sheet comprising ribs laterally spaced from each other by a pan or trough section, each rib being of a hollow mushroom shape in cross-section, having a head and a stem which narrows to the head, and a sealing device located between the ends of the overlapping profiled roof sheets wherein the sealing 20 device has an elongate body which has upper and lower longitudinal surfaces and laterally outwardly facing longitudinal side surfaces, the sealing device having at one or more locations along its length an engagement portion at which the upper surface is raised, and at which the lower surface is raised, and is recessed, and wherein each of the lower and the upper surfaces of the 25 engagement portion has a respective form which at least in part corresponds to the form in cross-section of the outer, upper surface and the inner, lower surface of the ribs of the longitudinally overlapping profiled roof sheets, wherein the raised lower surface of the sealing device engages with a rib of a lower first one of the overlapping sheets and a rib of a second, upper one of 30 the overlapping sheets engages with the raised upper surface of the sealing device, with the body of the device engaging each sheet laterally to at least one side of the ribs thereby providing a seal between the ends of the overlapping roof sheets. 857307 speci (clean) 10 July 09 3 At least in preferred forms, the sealing device enables the provision of a step between the ends of overlapping roofing sheets which is substantially less than 1 00mm in height. Also, at least in preferred forms, the sealing device facilitates 5 the provision of a waterproof joint between the ends of overlapping roofing sheets, even in roofing having a fall for rainwater run-off as low as about 1 . The lower surface of the sealing device enables the sealing device to be pressed down onto and engage with a rib of a lower first one of the 10 overlapping sheets, while the raised surface enables the second, upper one of the overlapping sheets to be pressed down onto the device to engage a rib of the second sheet with the raised upper surface of the formation, with the body of the device engaging each sheet laterally to at least one side of the ribs. Thus, the device is able to provide sealing between the ends of the 15 overlapping sheets by the engagement portion being engaged with and sealing at a rib of each of the sheets, with the body providing a seal between a pan section of the sheets laterally from the ribs. For the overlapping sheets, a respective sealing device may be used to 20 engage and provide sealing between each of successive pairs of overlapping ribs of the sheets. In that case, the longitudinal extent of the body of each device preferably is such that the ends of successive devices are able to abut to provide a seal for the overlapping sheets between abutting ends of successive devices. The abutting ends may inter-fit to assist in providing the 25 seal. However, as an alternative, the body of the sealing device may have a length, and a respective engagement portion for each successive pairs of overlapping ribs of the sheets, to enable a seal to be provided by one sealing device 30 across the full lateral extent of the overlapping sheets. In each case, the seal able to be achieved most preferably results from the body of the sealing device bearing against a pan or trough of each sheet, between the successive pairs of 857307 speci (clean) 10 July 09 4 overlapping ribs, with each engagement portion providing a seal in each of overlapping ribs of the sheets. While a given roof may have only a single line of longitudinally successive 5 sheets, it is more usual for there to be at least two laterally adjacent lines of sheets, with side edge margins of the sheets of one line overlapping and sealingly inter-fitting with side margins of the sheets of the next adjacent line. It is preferred that a seal provided between the overlapping ends of successive sheets of one line is continuous across the in-line overlapping ends of sheets 10 of the next adjacent line. This can be achieved by an end of a sealing device for the one line abutting an end of a sealing device for the next line, with the abutting ends preferably inter-fitting. Alternatively, a single sealing device may provide a seal between the ends of the sheets of each of two or more lines. 15 It is possible for a single sealing device to provide a seal across in line overlapping ends of all of two or more lines of sheets, such as across the full width or lateral extent of a roof. However, this can create installation difficulties, and give rise to a risk of the device being damaged or being incorrectly installed. It generally is most convenient if the longitudinal extent of the body of 20 the sealing device corresponds substantially to the width or lateral extent of the sheets. The sealing device can be made for a number of arrangements. As indicated, in one arrangement there may be a respective device for each overlapping pair 25 of ribs of a line of sheets while, in another arrangement, a single device may extend across each overlapping pair of ribs of a line, or of two or more laterally adjacent lines. However, successive devices preferably abut and most preferably are inter-fitted. 30 Accordingly, in an embodiment, the surface cladding system includes a series of successive sealing devices wherein the ends of the successive sealing devices inter-fit. 857307 speci (clean) 10 July 09 5 Also, an arrangement of a single device which extends across each overlapping pair of ribs of the sheets of a single line is preferred. In the following, an arrangement using a single device for each overlapping pair of ribs for a single line of sheets is assumed, although much of the description of 5 that single device is applicable to the other arrangements for the device. In a usual form of profiled sheet for roofing, the side margins are of an interfitting form such that laterally adjacent sheets co-operate to form a profiled rib. 10 Intermediate of the side margins, the sheet has at least one profiled rib which is spaced from a side margin or a next adjacent rib by a pan or trough of a standardised width. The arrangement is such that, with the sheets installed in lines which inter-fit at side margins, the appearance is of a uniform array of 15 parallel profiled ribs substantially uniformly spaced by pans or troughs. A preferred form of sealing device is consistent with this in that the sealing device has: a) a body of a length corresponding substantially to the width between side edges of the profiled sheet with which it is to be used; 20 b) respective end portions of the body each able to abut end wise an end portion of another in-line sealing device so the abutting end portions have the form of a engagement portion; c) intermediate of the end portions, at least one engagement portion; and 25 d) a spacing portion of the body by which one engagement portion is spaced from an end portion or a next adjacent engagement portion. The arrangement is such that an end to end series of the sealing devices have the appearance of a uniform series of engagement portions substantially 30 uniformly spaced by spacing portions of the bodies. In an embodiment the lower surface of the engagement portion has re-entrant shoulders that locate under the head of a rib. With the device engaged on a 857307 speci (clean) 10 July 09 6 lower one of the overlapping sheets, the re-entrant shoulders defined in each head section of formation locate under the head of a respective rib of the lower one of the overlapping sheets. 5 The raised upper surface and the recessed lower surface of engagement portions preferably have substantially complementary forms. That complementary form preferably is exhibited by the abutting end portions of inline sealing devices when they are abutting endwise. The complementary forms most preferably correspond substantially to the cross-sectional profile of 10 the lower, inner surface and the outer, upper surface, respectively, of profiled ribs of the profiled sheets. One form of rib provided on roofing sheets defines a channel which is of a re entrant shape in cross-section. The channel has at least one shoulder which 15 faces away from the opening to the channel. Thus, the channel is able to be pressed down onto a clip, for retaining the sheet on a supporting roof framework, to locate a cleat formation of the clip beyond and against the shoulder. In embodiments disclosed herein, the rib is of a hollow mushroom shape in cross-section, having a head and a stem which narrows to the head. 20 Thus, as the sheet is forced down onto a clip of a somewhat complementary form, the cleat formation of the clip forces side walls of the rib apart until the cleat formation enters the head. The side walls then are able to recover to their initial spacing, to retain the cleat formation in the head, with a respective shoulder defined by each side wall of the rib, at the underside of the head, 25 resisting separation of the sheet from the clip. Preferably there is a similar relationship between the engagement portion of the sealing device and the form of ribs of roofing sheets with which the sealing device is to be used. The body of the sealing device may have a level of resilience by which it is 30 able to deform elastically between overlapping sheets and thereby provide a seal with each sheet along the length of the body of the sealing device. To enable this, the body of the device may be partly or wholly formed of a resilient material, such as a resilient plastics material, preferably a foam of a synthetic 857307 speci (clean) 10 July 09 7 plastics material. Where the resilient material is a foam, it preferably is a closed cell foam, such as of a ethylene propylene diene monomer or of a polyamide. While resilient, the body of the sealing device preferably is sufficiently stiff as to sufficiently resist compression as the upper sheet is 5 pressed down onto the sealing device, and thereby provide a positive pressure against each of the sheets for effective sealing between the sheets. Subject to the chosen material, the body of the sealing device and its at least one engagement portion may be formed entirely of the one resilient material, 10 such as a foam material. Accordingly, in an embodiment of the invention, the body of the sealing device and its at least one engagement portion is formed entirely of a resilient material such that the sealing device has a level of resilience by which it is elastically 15 deformed between the overlapping roof sheets and thereby provides a seal with each sheet along the length of the body of the sealing device. However, it can be beneficial for the sealing device to include along its length a relatively more stiff reinforcing member, such as for stiffening resilient material 20 of the body. The sealing device may, for example have adjacent layers of foam or other resilient material and reinforcing material. Thus, in a first form, one of the side surfaces of the body may be defined by a layer of a resilient material, with the other side surface defined by a reinforcing member. In a second form, the sealing device has three layers, with the side surfaces defined by a 25 respective layer of resilient material secured to an intermediate layer forming the reinforcing member. In a third form, a single layer of resilient material is secured between respective reinforcing members each defining a respective side surface. In each of those forms, the width of the or each layer of foam or other resilient material, between the upper and lower surfaces of the body of 30 the sealing device, exceeds that of the or each reinforcing member to enable the resilient material to be compressed to provide a seal between overlapping sheets. 857307 speci (clean) 10 July 09 8 In an alternative form, each of the upper and lower surfaces of the body of the sealing device is defined by a respective layer of foam or other resilient material. In that form, the body has reinforcing member intermediate of the layers of resilient material, preferably with those layers secured directly to the 5 reinforcing member. Overlapping roofing sheets are secured to a roof frame at locations other than where they overlap using roofing clips. The sealing device of the invention enables a short length of overlap between sheets, such as of about 180 to 10 220mm. As a consequence, the sheets can be adequately secured relative to each other at their overlap by a respective roof clip for each sheet just beyond that overlap. In that case, the sealing device does not need to provide for securement between the sheets at their overlap. Rather, the sealing device may principally or solely provide sealing between the sheets. However, despite 15 this, it is preferred that the at least one engagement portion of the body of the sealing device is adapted to strongly engage with each of the overlapping ribs. To enable this, the engagement portion preferably includes a cleat structure of a relatively rigid material and able to achieve a snap-fit engagement with each of the ribs and thereby assist in securing the overlapping sheets together. 20 Accordingly, in an embodiment of the invention, the surface cladding system includes a cleat structure of relatively rigid material in snap-fit engagement with overlapping ribs of the overlapping roof sheets. 25 The cleat structure may have a form corresponding at least partially to that of the engagement portion. The cleat structure may be incorporated within the engagement portion, or it may be secured against at least one side face of the engagement portion. In one convenient arrangement, the cleat structure has a respective cleat part secured against each side face of the engagement 30 portion. In that arrangement, at least one projection or pin may extend through the engagement portion to engage and to secure the cleat parts in assembly. Alternatively, each cleat part may be securely bonded to a respective side of the engagement portion. 857307 speci (clean) 10 July 09 9 The cleat structure may be made of a rigid engineering plastics material. In the case of a cleat structure having cleat parts secured in assembly by a projection or pin, the projection or pin may be formed integrally with a cleat part. 5 Alternatively, the cleat parts may be secured in assembly by a projection or pin applied through each of the cleat parts. The cleat parts may be formed of a metal, such as sheet steel. If having two cleat parts, those parts may be secured in assembly by any suitable form of projections or pins, such as rivet pins. A modified form of cleat structure can be provided at abutting ends of 10 longitudinally in-line sealing devices. While the cleat structure may be similar overall to the forms described above, it preferably is secured in place once the ends are abutting. Also, the cleat structure preferably includes a linking member which secures the cleat structure to each of the abutting ends. 15 Brief Description of the Drawings In order that the invention may more readily be understood, reference now is directed to the accompanying drawings, in which: Figure 1 is a perspective view showing part of a roof frame with 20 overlapping roof sheets of a roofing system; Figure 2 is similar to Figure 1, but shows enlarged detail of a sealing device between overlapping ends of the roof sheets; 25 Figure 3 shows, in a partially exploded end elevation, enlarged detail of a connection in the system of Figures 1 and 2, illustrating a first embodiment of a sealing device; Figure 4 shows a perspective exploded view of the connection of Figure 30 3; Figure 5 is a perspective view of a second embodiment of a sealing device; 857307 speci (clean) 10 July 09 10 Figure 6 is an exploded perspective view of the device of Figure 5; Figure 7 is a perspective view of a third embodiment of a sealing device; 5 Figure 8 is an exploded perspective view of a modified form of the device of Figure 7; Figure 9 is a perspective view of a fourth embodiment of a sealing 10 device; Figure 10 is a side elevation of the device of Figure 9; Figure 11 is an exploded perspective view of the device of Figure 9; and 15 Figure 12 is a perspective view of a fifth embodiment of a sealing device. Detailed Description 20 The views of Figures 1 and 2 show two longitudinally in-line roof sheets R1 and R2, shown truncated in Figure 1, and very much shortened in Figure 2 to show essentially only that part of sheets R1 and R2 at and adjacent to their overlap. The sheets R1 and R2 are mounted in relation to a C-section purlin P comprising part of a roof frame (not otherwise illustrated). The roofing of which 25 sheets R1 and R2 form part is inclined downwardly to the left so that rainwater will drain to sheet R1 from sheet R2. The upper end of sheet R1 is secured on purlin P by a connector C. A strap S of connector C is secured along the top surface of purlin P, while a number of 30 uniformly spaced clips C1, C2 and C3 are mounted on the strap S. The connector C shown in Figure 1 is provided for a second sheet R1 to be laterally adjacent the sheet R1 shown, with the laterally adjacent sheets having 857307 speci (clean) 10 July 09 11 inter-fitting side margins. The second sheet R1 would be installed before sheet R2, but has been omitted for ease of illustration. The lower end of sheet R2 overlaps with the upper end of sheet R1 and a 5 sealing device D, shown more clearly in Figure 2, provides sealing between the overlapping ends of sheets R1 and R2. Below purlin P along sheet R1, sheet R1 is similarly connected to other purlins by respective connectors C while, above purlin P along sheet R2, respective connectors C will connect sheet R2 to other purlins. Also, unless sheet R1 is the lowermost sheet or 10 sheet R2 is an uppermost sheet, its other end will similarly overlap with a further sheet. Each sheet R1 and R2 has laterally spaced ribs 10 spaced from each other by a pan or trough 12. The side margins of laterally adjacent sheets are profiled 15 and inter-fit to form a composite rib (not shown) of the same form as ribs 10. The spacing between ribs 10 and between the composite ribs and the closest rib 10 is uniform and corresponds to the spacing between clips C1 to C3 of connector C. 20 As shown in Figure 3, the sheet R1 is able to be pressed down onto the connector C to locate, and lock, each of clips C1 to C3 in a respective channel or groove 14, shown in Figure 4 as defined by the respective ribs 10 and the composite rib. As can be appreciated most readily from Figure 4, the ribs 10 are of a mushroom shape as seen in end elevation. The ribs 10 have side 25 walls 6 in which the groove 14 tapers inwardly towards a head 18 within which the groove 14 has re-entrant shoulders 20. Each of the clips C1 to C3 is of a complementary form to groove 14, in having a stem portion 22 which tapers inwardly away from strap S to an enlarged head 24. As sheet R1 is pressed down onto connector C, the head 24 of each of clips C1 to C3 enters a 30 respective groove 14 and forces apart the side walls 16 of the rib 10. The head 24 of the clip is able to enter the head 18, after which the walls 16 recover to position shoulders 20 behind head 18 and thereby hold the rib 10 captive on the clip C. With sheet R1 locked down on purlin P by connector C, 857307 speci (clean) 10 July 09 12 the sealing device D then is able to be pressed down onto, and engaged with, sheet R1. The sheet R2 then is able to be pressed down onto, and engaged by the sealing device D. 5 As can be seen in Figures 3 and 4, the device D has an elongate body sections B which have upper and lower surfaces 26 and 28, and respective sides 29 which extend between surfaces 26 and 28. Also, at spaced centres corresponding to the spacing between centres for ribs 10, the device D has upstanding engagement portions or formations F. The formations F provide 10 raised parts 26a of the upper surface, and recessed parts 28a of the lower surface, of body B. As can be appreciated from Figure 4, the lower surface 28 of the body B of device D as viewed in side elevation is substantially the complement of the 15 upper surface of sheet R1, while the upper surface 26 is substantially the complement of the lower surface of sheet R2. Thus, as shown in Figure 4, the engagement formations F have a mushroom-like shape in side elevation, provided by legs 30 which converge, away from body B, to an enlarged head section 32. The recessed part 28a defines a recess defined by the spacing 20 between legs 30 and the interior of head section 32, while the raised part 26a of surface 26 is similar in form to a rib 10 and is defined by the outer surface of legs 30 and the exterior of head section 32. As a consequence, the device D is able to be pressed down onto lower sheet R1 to enable the head 18 of each rib 10 of sheet R1 to be received in a recessed part 28a within a respective 25 formation F. The head 18 of rib 10 is able to pass between legs 30 to locate in head section 32 of formation F. Thus, device D is able to be engaged on sheet R1 in a manner analogous to the securement of sheet R1 on purlin P by connector C. As device D is pressed onto sheet R1, the head 18 of each rib 10 resiliently deforms the legs 30, to enable the head 18 to be received in the 30 enlarged head section 32, after which the legs recover to contact walls 26 of rib 10. 857307 speci (clean) 10 July 09 13 Similarly, as also shown in Figure 4, sheet R2 is able to be pressed onto device D to enable each head section 32 of each formation F to be received within a groove 14 of a respective rib 10 of sheet R2. For this, the walls 26 of the ribs 10 of sheet R2 pass down over and resiliently compress the head 5 section 32, until the head section 32 is received into the head 18 of the rib and recovers to locate behind shoulders 20. Thus, sheet R2 is able to be engaged on device D in a manner analogous to the securement of sheet R1 on purlin P by connector C, such that sheet R2 is in overlapping relation to sheet R2. To a degree, device D is secured on sheet R1 once sheet R2 is installed. However, 10 sheets R1 and R2 are secured in relation to each other by connector C securing sheet R1 to one side of device D and a further connector located to the other side of device D and securing sheet R2. With the device D engaged on sheet R1, the re-entrant shoulders 34 defined in 15 each head section 32 of formation F locate under the head 18 of a respective rib 10 of sheet R1. This acts to resist device D from lifting from sheet R1. Also, with sheet R2 secured on device D, the re-entrant shoulders 20 in each head 18 of the ribs 10 of sheet R2 locate under the head section 32 of the respective formation F. This similarly acts to resist sheet R2 from lifting from 20 device D. Also, in being constrained on a rib 10 of sheet R1 by location within a rib 10 of sheet R2, deformation of formations F is resisted, securing the assembly of sheets R1 and R2 and device D therebetween. Despite this, it is respective connectors C which secure the overlapping ends of sheets R1 and R2 in relation to each other. 25 Figures 3 and 4 are provided primarily for the purpose of illustrating how a seal between the overlapping ends of sheets R1 and R2 is provided by the sealing device D. However, it also will be noted that device D is strengthened at each formation F by what, in Figures 5 and 6, is referred to as cleat structure having 30 a respective part at each side of body B. The cleat structures are stiff or rigid and will be understood from description of other embodiments subsequently detailed herein. As with some of those embodiments, the parts of each cleat structure are inter-connected by pins extending laterally through body B. Also, 857307 speci (clean) 10 July 09 14 abutting ends of successive devices D can be inter-connected by such a cleat structure. The device D may have a body B of a length corresponding substantially to the 5 width of the roofing sheets with which it is to be used. Alternatively, the body B may be built up of successive end to end abutting modules which are secured together by a cleat structure. Figures 5 and 6 show a sealing device Dl according to a second embodiment. 10 The device Dl has an elongate body B1 which has upper and lower surfaces 126 and 128 and respective outwardly facing sides 130. The body B1 is made up of three layers which comprise side layers 40 and an intermediate layer 42 between layers 40. The layers 40 and 42 have a similar form except that layer 42 is slightly oversized so as to stand proud of layers 40 along the upper and 15 lower surfaces 126 and 128, and at the ends of device Dl. At uniform distances along body B1, the device Dl has engagement portions or formations Fl. The device Dl has two complete formations Fl intermediate of its ends. Also, at each end, device Dl has a respective half formation Fla 20 which is able to form a complete formation Fl with a half formation of another device Dl. In side elevation, each complete formation Fl, and each formation Fl which results from end to end abutting devices Dl, has a shape at upper surface 126 which corresponds substantially to the shape in cross-section of a rib 10 of sheets R1 and R2 and, hence, is substantially the complement of the 25 shape in cross-section of the channel or groove 14 of a rib 10. Also, in side elevation each complete formation Fl, and each formation Fl at such abutting ends, has a shape at lower surface 128 which corresponds substantially to the shape in cross-section of a channel or groove 14 of a rib 10 and is the complement of the shape in cross-section of a rib 10. Thus, each formation Fl 30 has upwardly converging legs 130 and a hollow head section 132, while each half formation Fla has one leg 130a and a part 132a of a head section 132. 857307 speci (clean) 10 July 09 15 At each complete formation Fl, there is a cleat structure which is made of a relatively rigid material and has a respective part 46 and 47 at each side of the body B1. The parts 46 and 47 each have a form similar to that of the formation Fl in that they have legs 46a and 47a which converge towards an enlarged 5 head portion 46b and 47b. The part 46 has projections 46c which are inserted through holes formed in formation Fl and into holes 47c formed in part 47 in which they are secured; there being two projections 46c extending from head portion 46b and one projection 46c from the end of each leg 46a remote from head section 46b. The parts therefore are secured in assembly on body B1. 10 The legs 46a and 47a of parts 46 and 47 converge to the enlarged head portions 46b and 47b so that, like the formation Fl and the ribs 10 of sheets R1 and R2, the parts 46 and 47 are somewhat mushroom shaped. Each layer 40 of body B1 may be secured to a respective face of layer 42 by 15 adhesive bonding. They alternatively, or additionally, may be secured by pins 43 shown in Figure 6 which are inserted laterally through body B1, with the pins being retained by having an enlargement at each end. The layers also are held by the engagement, between parts 46 and 47, provided by projections 46c of part 46 engaging in the holes 47c of part 47. 20 The layers 40 and 42 of device Dl may be formed of a first resilient material, such as a foam plastics material, with each layer 40 being of a stiffer resilient material, such as a more rigid foam and, hence, less readily compressible than the material of layer 42. The parts 46 and 47 of structure 44 may be of a 25 flexible, but relatively stiff engineering plastics material so that parts 46 and 47 reinforce the formation F and limit the extent to which they are compressible. The head section 49 of each of parts 46 and 47 is dimensioned so that, as sheet R2 is pressed down on device Dl, section 49 initially forces the walls 26 of the ribs 10 of sheet R2 apart, and allows the walls to recover when section 30 49 is within head 18 of the rib 10, behind the shoulders 20. One of the half formations Fla also has a cleat structure 44 which is substantially the same as the structure 44 at the complete formations Fl. 857307 speci (clean) 10 July 09 16 However, the projections 46c of part 46 securing parts 46 and 47 together extend through only the half formation, from head section 46b and to head section 47b. Also, the half formation Fla also includes a U-shaped member 50, having parallel arms 50a joined by a web section 50b. The arms 50a 5 correspond to projections 46c in form and function. The arms 50a are spaced by portion 50b so that each arm is able to extend through the end of each leg 46a remote from head section 46b to the other cleat part 47. Member 50 is fitted and secured when two devices Dl are in abutting end to end relationship, with each arm 50a extending through a half formation Fla of a 10 respective device Dl, to secure the devices Dl in that relationship. Figures 7 and 8 show respective devices D2 which are sufficiently similar to enable them initially to be described in the same terms. However their differences also will be discussed later herein. Also, the devices D2 are similar 15 in overall form and function to device Dl of Figures 5 and 6, and the initial description of them first will deal with the features by which they each differ from device Dl. The principal difference between each device D2 and the device Dl is that the 20 devices D2 are made up of repeated modules, of which three are illustrated and distinguished as modules Ml, M2 and M3. However, the number of modules can be varied as required. Also, as provided for use, the devices D2 can be pre-assembled, as shown in Figure 7, in a required standard length. 25 In the devices D2, each of modules Ml, M2 and M3 is of the same form and includes a respective unit U forming part of the overall body B2, and a respective cleat structure 144. However, the structure 144 is of unitary or integral construction, with parts 146 and 147 connected by a bridging member 52. The formations F2 are created by the modules Ml, M2 and M3 abutting in 30 end to end relation in a manner resulting in the member 52 being enclosed between the abutting ends of successive modules, within the head section of a formation F2. As shown in Figure 8, the half formations to produce the formations F2 are recessed at 132a to accommodate member 52. 857307 speci (clean) 10 July 09 17 The unitary structures 144 of each device D2 receives the end formations of abutting end to end units U between a respective half of the opposed parts 146 and 147. The units U then are secured by screws or rivets 53 which pass 5 through one of parts 146, 147 and through holes 54 in the unit U to the other one of parts 146, 147. The devices D2 differ from each other principally in the material and fabrication of the respective structures 144. In the case of Figure 7, the structures 144 10 are formed of stiff, but resilient steel, such as a spring steel, shaped and folded to the required configuration. In the case of Figure 8, the structures 144 are made of a stiff, but resilient engineering plastics material, such as polypropylene, polystyrene acrylonitrile or a polyamide, such as by injection moulding. 15 In relation to each of Figures 7 and 8, it is to be appreciated that each of modules M1, M2 and M3, comprising a part of the overall body B2 in the form of unit U, plus a cleat structure 144, itself is a sealing device according to the invention. That is, the overall sealing device D2 according to the invention is 20 an assembly of end to end connected smaller sealing devices each according to the invention. Figures 9 to 11 show a device D3 which is similar to device D1 of Figures 7 and 8. The principal difference is that of the parts 246 and 247 of structure 25 244 are secured in assembly by an integral bridging member 152, which extends between the head sections 246b and 247b. Also, parts 246 and 247 are secured on body B3 by U-shaped members 250 similar to members 50 shown in 5 and 6. A respective pair of members 250 is used for each structure 244. However, the arms 250a are joined by web section 250b, and one arm 30 250a of each member 250 extends between the head sections 246b and 247b of parts 246 and 247, while the other arm 250a extends between the ends of legs 246a and 247a remote from sections 246b and 247b. 857307 speci (clean) 10 July 09 18 At one end face, device D3 is provided with a recess 232a. The other end face is provided with a protrusion (not shown) which has a shape complementary to that of recess 232a. This facilitates close inter-fitting between abutting ends of a number of devices D3 assembled end to end. 5 Figure 12 shows a device D4 which is similar to device D1 of Figure 5. However, device D4 is of unitary, integrally moulded form, having opposite ends of complementary form-enabling a number of devices D4 to be assembled end to end. 10 Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention. 857307 speci (clean) 10 July 09