WO1998021705A1

WO1998021705A1 - Replacement sign system

Info

Publication number: WO1998021705A1
Application number: PCT/US1997/020581
Authority: WO
Inventors: Ulf Normann Olsen
Original assignee: Minnesota Mining And Manufacturing Company
Priority date: 1996-11-12
Filing date: 1997-11-12
Publication date: 1998-05-22
Also published as: GB9623516D0; GB2319386A

Abstract

A kit is described for mounting to a sign including flexible sign sheeting. The kit includes a length of pre-formed or formable profiled material having a first and a second end. The profile material includes at least one longitudinal channel portion to receive edge portions of at least the sign sheeting. The channel portion preferably surrounds the edge portions of the sign sheeting andthe backing member. The profiled material also has first and second complementary joining pieces adjacent the first and second ends, respectively. A tamper-proof clamping device is provided for clamping together a pair of complementary first and second joining pieces. The kit may include a backing member which is preferably thermally insulating and compressible. A method of installing the sign kit to an existing sign is described.

Description

REPLACEMENT SIGN SYSTEM

Technical Field

The present invention relates to signage, in particular to a replacement sign system which may be used for traffic signs, a kit for mounting signs and a method of refacing an existing sign.

Background of the Invention

Roadway signs generally consist of three components, a sign face and a suitable backing material for the sign face and a mounting device for mounting the sign to a sign post. Sign faces may include retroreflective material which may be fluorescent. The backing material is conventionally a metal, such as aluminium sheet, fibre glass reinforced plastic, or laminated aluminium honeycomb panels. Some designs make use of extruded aluminium profile for the backing in which there are suitable slots for attachment to a sign post.

When a sign wears out, it is usually replaced or refurbished. Reasons for replacing or refurbishing highway signs are sign face deterioration (such as cracking, delamination, missing letters, discoloration, etc.); vandalism (such as spray paint, bullet holes, theft, etc.); knock down, structural damage, or sign face damage (due to collisions, projectiles, etc.); excessive dirt or grime; poor retro-reflectivity or a loss of fluorescent property; or because the structural integrity of support structure has deteriorated.

The most common methods of refurbishing existing signs are the use of overlay panels attached in the field, commercial overlays, and cleaning/re-coating of panels. The overlay usually consists of a sign face attached to a sheet aluminium substrate, although plywood or plastics can be used as well. An overlay is usually fastened in the field in the existing sign by rivets or sometimes rivets and adhesive. These overlay panels tend to produce a wavy surface on the sign, especially at the rivet locations. Commercial overlays consist of reflective sheeting attached to a thin,

aluminium backing, coated with a pressure sensitive adhesive. It is applied directly over an old panel after the legend/border has been removed, using a rubber roll or cloth. No fasteners are required, but the process takes more time and care than the field-installed overlays.

A third method of refurbishing, cleaning or re-coating of panels involves removal of the old sign, removal of the old sign legend, washing and polishing of the background, possible re-coating of the panel, and attachment of a new sign surface.

Replacement of the sign face requires removal of the entire sign which is more expensive in most cases and is heavy and difficult for one person. Further, it is difficult to carry out the removal and replacement of large signs in windy conditions. Due to rusting of fasteners or supports, damage may be done to these during removal. The design may also not allow replacement of the sign without permanent damage, for example where rivets are involved.

All forms of sign replacement or repair may need diversion of traffic causing added expense, time and inconvenience to motorists and some danger to the persons working on the sign.

Figure 1 shows one type of conventional sign frame which consists of a profiled metal piece 2 which includes two hollow profiles 8 and 9. Hollow profile 9 is used for placement of a sign sheeting material 7 and a backing plate 6 which may be of metal. Hollow profile 8 is used for clamping to the signpost by suitable clamping means. An alternative to the design shown in Figure I is shown in Figure 2 in which the central wall 4, which is shared by both profiles 8 and 9, may be crimped against back of the sign backing material 6 so as to prevent backing material 6 and sheeting 7 from moving about within the hollow profile 9. In both Figures 1 and 2, the profile 2 may be a single piece of profile which is shaped to the outer edges of the backing plate 6 and sheeting 7 and the free ends of profile 2 may be joined by a small piece of metal in hollow profile 8 which bridges the two cut ends of profile 2 and which is connected to profile 2 on both sides by riveting. This type of sign frame is not easy to remove. Any method of removal requires drilling out the rivet holes causing damage to the frame which may result in the frame being discarded.

The use of two profiles to secure a sign is known from DE-OS 1958667. A similar profile is known from DE-U-9110340. A different type of U-shaped profile for securing a sign is known from DE-U-8913318, in which the sign may be slotted into a pre-formed, rectangular frame. Another rectangular frame is known from DE-U- 8509600 in which a series of plates or spaces may be located into a fixed one-piece rectangular frame.

Flexible sign sheeting material may be secured in accordance with the device shown in DE-OS-2735701 which includes two clamps for clamping the outer edges of a flexible material and stretching it in the longitudinal direction. A similar device is known from DE-OS-2735701.

Tamper proof sign mounting devices are known from U.S. Patent Nos. 4,891,895; 4,161,834; 4,583,309; and 4,228,425. The '895 patent describes a license plate holder which is secured by a tamper-resistant button head socket cap screw. The '834 patent describes a wall-mounted sign secured by a threaded member having a concealed anti-rotation device. The '309 patent describes a display assembly having a front frame and a back insert and a special tool to separate the two. The '425 patent describes a security plate with embedded electrical wires connected to an alarm system. The ends of the wires are concealed in a frame.

An object of the present invention is to provide a system of refurbishing signs which is quick and easy to carry out and provides a new, environmentally protective sign.

Summary of the Invention

The present invention includes a kit for mounting a sign comprising: at least a flexible sign sheeting; a length of pre-formed or formable profiled material, said profiled material having a first and a second end, said profiled material including: at least one longitudinal channel portion to receive edge portions of said sign sheeting; and first and second complementary joining pieces adjacent said first and second ends, respectively; and a tamper-proof clamping device for clamping together a pair of complementary first and second joining pieces.

Preferably the channel portion surrounds the edge portions of a suitable backing member and the sign sheeting to protect the sign sheeting from the environment. Preferably the backing material is made from a compressible, thermally insulating material.

The invention also includes a refurbished sign including an existing sign having an existing sign face, said refurbished sign comprising: a flexible sign sheeting covering said existing sign face; a length of profiled material, said profiled material having a first and a second end, said profiled material including: at least one longitudinal channel portion receiving edge portions of said sign sheeting and at least said existing sign face, and first and second complementary joining pieces adjacent said first and second ends, respectively; and a tamper-proof clamping device clamping together a pair of complementary first and second joining pieces.

The invention also includes a method of refacing an existing sign having an existing sign face, comprising: covering said existing sign face with a flexible sign sheeting; installing a length of profiled material around said existing sign, said profiled material having a first and a second end, said profiled material including: at least one longitudinal channel portion receiving edge portions of said sign sheeting and at least said existing sign face, and first and second complementary joining pieces adjacent said first and second ends, respectively; and clamping together a pair of complementary first and second joining pieces using a tamperproof clamping device.

The invention may provide the advantage of an economical tamperproof replacement sign kit. The invention may also provide the advantage that the replacement kit can be applied quickly to road signs thus reducing outage times on roads. The invention may also provide the advantage that the replacement kit may be used on a variety of sign shapes. The dependent claims define further embodiments of the invention.

Brief Description of the Drawings

The invention, its advantages and embodiments will be described with reference to the following drawings, in which:

Figures 1 and 2 show cross-sections through conventional sign frames. Figure 3 shows a first embodiment of the present invention.

Figure 4 shows a cross-section through a sign frame in accordance with a first embodiment of the present invention.

Figure' 5 shows a cross-section through a sign frame of a second embodiment in accordance with the present invention. Figure 6 shows a more detailed view of a tamper-proof clamping device in accordance with the present invention.

Figure 7 is a schematic view of the tool used to close the tamper-proof clamping device in accordance with the present invention.

Figure 8 shows a more detailed view of a further tamper-proof clamping device in accordance with the present invention.

Figure 9 shows a schematic diagram of an existing signpost with a sign.

Figure 10 shows the existing signpost fitted with a sign frame and sign in accordance with the present invention.

Description of the Invention

In the attached drawings some of the thicknesses and dimensions have been exaggerated in order to improve their clarity. The invention is described with respect to certain specific embodiments as illustrated by the figures. The invention is not limited thereto but only by the claims.

Figure 3 is a schematic representation of a first embodiment of the present invention. A sign 17, which may include fluorescent or retroreflective materials, is surrounded by a sign frame 12 having complementary end joining pieces 18, 20 which ^~ may be joined together in a tamperproof manner. Frame 12-with complementary edge portions 18, 20 should preferably surround the complete periphery of sign 17. Tamperproof in accordance with this application means designed such as to prevent unauthorised entry by a person carrying simple tools such as a screwdriver within a significant amount of time which may raise suspicion such as 5-10 minutes. End joining pieces 18, 20 may include holes 19, 21 respectively for receipt of a locking device (not shown). Frame 12 may be made from any suitable rigid material. It is preferred if frame 12 is made of an elastic, formable or ductile material, such that the end joining pieces 19, 20 may be separated to a sufficient distance to be able to apply and remove frame 12 from the sign 17. The invention is not limited to the circular sign shown in Figure 3 but may be applied to rectangular, square, triangular or any other shape of sign.

Figure 4 shows a cross-section through frame 12. The frame 12 includes at least one profiled channel 9 which may be U-shaped or V-shaped in such a manner that edge portions of a backing member 16 and a flexible signage sheeting 17 may be slid into the channel. Optionally, a backing plate 11 may be included so that the backing member 16 is located in the channel, sandwiched between the plate 11 and the signage sheeting 17. It is preferred if channel 9 envelopes the edge portions of backing member 16, flexible sheeting 17 and optional backing plate 11 to seal the edge portions against the environment. More preferably, the dimensions of channel 9 and backing member 16, flexible sheeting 17 and optional backing plate 11 are selected so that the edge portions thereof fit snugly into channel 9 and are protected by the frame 12 from rain and water spray from cleaning equipment. Channel 9 may be bounded by two walls 14, 15 which are spaced apart at sufficient distance as to be able to receive backing number 16, signage sheeting 17 and optional backing plate 11. Preferably, the ends of the channel 14' and 15' are formed in such a way that backing member 16 and signage sheeting 17 may be introduced into channel 9 without difficulty. For instance, the ends 14' and 15' may be chamfered, rounded or tapered in such a way as to provide guidance for backing member 16, signage sheeting 17 and backing plate 11 on entry into channel 9. Optionally, additional profile elements such as channel 8 including additional wall 13 may be provided in frame 12 for attachment purposes. The invention is not limited to the particular form of channel 8 shown in Figure 4 but may be adapted to suit different clamping systems and mechanical arrangements. Frame 12 is preferably a single piece of channel shaped appropriately. Frame 12 may be made up of several pieces which are joined together to form the complete frame 12.

Backing material 16 may be any suitable backing material such as plastics, (including PVC, ABS, polycarbonate, polypropylene, polymethylmethacrylate); wood (such as plywood); hard elastomeric materials (such as rubbers); or metal. Backing plate

11 is preferably made from a rigid material such as a metal (for example aluminum). Certain signage sheetings 17 may have reduced reflective properties when a surface film of moisture exists on the surface of the sheeting 17. This may occur, particularly at dawn and dusk, when the temperature of the sheeting is colder than the ambient air. This temperature difference can be caused by radiation loss from the sign post lowering the temperature of the sign post and influencing sheeting 17. For this reason, it is advantageous to isolate signage sheeting 17 thermally from the sign post and/or backing plate 11. It is particularly preferred if backing material 16 has thermal insulation properties in order to insulate signage sheeting 17 from the sign post to which the sign may be fixed. It is preferable if backing material 16 is a foamed polymeric material whereby the foam may be open or closed cell. Closed cell polymeric foams are preferred. Examples of a suitable foams are polyurethane or neoprene rubber foams. Suitable foam materials will be apparent to a skilled person.

It is also preferable if backing material 16 and signage 17 have a low thermal capacity. When backing member 16 and signage sheeting 17 have a low thermal capacity, the temperature of these two items will follow the air temperature more closely so that the chance of condensation on the surface of signage 17 may be reduced.

It is preferred if backing member 16 is compressible or elastically compressible.

Suitable materials may be the polymeric foams mentioned above such polyurethane or neoprene rubber foam. Is it advantageous if the backing plate 11 is made of a rigid material and the backing member 16 is made of a thermally insulating, compressible material such as foamed plastic or elastically compressible material such as foamed rubber. Due to the compressibility or elasticity of the backing member 16, minor changes in the dimensions of the channel 9 can be accommodated without leaving a gap between backing plate 11 or signage sheeting 17 and the walls 14, 15 of the channel 12.

Signage sheeting 17 may be retroreflective sheeting made by Minnesota Mining and Manufacturing Company, Minnesota, USA, for example: 3M Diamond Grade, 3M Engineer Grade, 3M High Intensity, embedded, encapsulated or enclosed lens reflective sheeting. Sheeting 17 may include retroreflective microspheres or cube comer arrays and may also include fluorescent or colored dyes in order to improve visibility of the sign. For example, such sheeting is disclosed in U.S. Patent numbers 4,648,932; 4,767,659; 5,064,272; 4,025,159; 5,450,235; and 5,138,488.

Sheeting 17 may be fixed to backing member 16 by means of suitable adhesives or other fixing methods. Although it is preferable to use a pressure-sensitive adhesive, any adhesive that is particularly suited to the particular substrate selected and end-use application can be used on the sheeting 17. Such adhesives are those known in the art any may include adhesives that are aggressively tacky adhesives, pressure sensitive adhesives, repositionable and/or positionable adhesives, hot melt adhesives and the like. Pressure sensitive adhesives are generally described in Satas, Ed., Handbook of Pressure

Sensitive Adhesives 2nd Ed. (Von Nostrand Reinhold 1989), the disclosure of which is incorporated by reference.

Pressure sensitive adhesives are particularly preferred. Particularly preferred are acrylate pressure sensitive adhesives commercially available from Minnesota Mining and

Manufacturing Company of St. Paul, Minnesota and generally described in U.S. Pat. Nos. 5,141,790, 4,605,592, 5,045,386, and 5,229,207.

Non-limiting further examples of pressure sensitive adhesives useful with the present invention include those adhesives described in U.S. Pat. Nos. Re. 24,906

(Ulrich); 2,973,826; Re. 33,353; 3,389,827; 4,112,213; 4,310,509; 4,323,557; 4,732,808; 4,917,929; and 5,296,277 (Wilson et al.) and European Publication 0 051 935, the disclosures of which are incorporated by reference herein. A presently ^~ preferred adhesive is an acrylate copolymer pressure sensitive adhesive formed from a 90/10 weight percent monomer ratio of 2-methylbutyl acrylate/acrylic acid in a 65/35 heptane/acetone solvent system (39-41% solids) and having an inherent viscosity of about 0.7-0.85 dl/g. Thickness of adhesive can range from about 0.012 mm to about 1 mm with a thickness of about 0.025 mm (1 mil) being preferred.

Figure 6 shows a schematic representation of a tamperproof clamping device in accordance with the present invention. End joining pieces 18 and 20 may be made out of any suitable material which may be fixed permanently to frame 12 by welding, including spot welding or ultrasonic welding, by adhesives, by casting or moulding in place or may be integrally manufactured with frame 12, e.g. by injection or transfer moulding of plastic, by casting such as aluminium die casting or by cold or hot forging or rolling. Suitable materials may be metals such as aluminium or galvanized steel or plastics.

End joining pieces 18, 20 each have one face which terminates substantially flush with the ends of frame 12 and these faces are arranged in such a way that end joining pieces 18, 20 may be closed together so as to form a continuous frame 12. To avoid space for access of a screw driver or similar implement, it is preferred if the abutting faces of end joining pieces 18, 20 meet across their area so that no gap is allowed for introduction of a tool. Advantageously, end joining pieces 18 and 20 include a bore 25 which is preferably a closed bore to avoid tampering from outside. Bore 25 is preferably located parallel to the closing direction of end joining pieces 18, 20 which, in accordance with the arrangement shown in Figure 6 is substantially parallel to the longitudinal direction of channel 9 of frame 12 at its ends.

End joining pieces 18 and 20 may be held together in a tamperproof manner by insertion of a pin, peg or dowel 22. Pin 22 may include a substantially cylindrical part 26 which may have a circular or polygonal cross section. Along one or more longitudinal faces of pin 22, protuberances 27 may be provided which form a interfering press-fit with the internal diameter of bore 25. The protuberances 25 may be forged into pin 22, may be cast therein, adhered thereto or manufactured by any other suitable method.

End joining pieces 18, 20 may include holes 19 and 21 respectively which run perpendicular to the longitudinal direction of channel 9 of frame 12. Holes 19, 21 may be used in conjunction with a tool to forcibly close end joining pieces 18, 20 against the frictional forces required to insert pin 22 into blind bores 25 of end joining pieces 18 and 20. One or more pins 22 and one or more blind bores 25 may be provided for joining end joining pieces 18 and 20.

Figure 7 is a schematic representation of a tool suitable for closing end joining pieces 18 and 20 as shown in Figure 6. The tool 30 includes two handles 31, 32 which may be 25 to 95 cm long and which are hingeably fixed by means of a bolt 35. Located at a short distance from bolt 35 are two pins 33, 34 which are firmly attached to handles 31, 32 by welding or by suitable screw thread and nuts. Pins 33, 34 are designed to engage with holes 19 and 21 of end joining pieces 18 and 20 respectively of frame 12.

Figure 8 is a schematic representation of another tamper-proof clamping device in accordance with the present invention. The tamper-proof clamping device as shown in Figure 8 may be made from the same materials as described with respect to Figure 6.

The same reference numbers in Figures 6 and 8 refer to the same components. End joining piece 48, 49 each have one face which terminates substantially flush with the ends of the frame 12 and the end joining pieces may be closed together to form a continuous frame 12. The end faces abut sufficiently that they do not provide access for a tool such as a screwdriver. One of end joining pieces 48, 49 includes a hole 42 which is preferably a blind hole to prevent tampering from outside. Fixed to, or part of one of the end joining pieces 48, 49 is a peg 43 which may have and outer serrated profile and is an interference press-fit into hole 42. Each of end joining pieces 48, 49 may have a hole 42 and a mating peg 43 (not shown). To provide further security a locking hole 41 and locking pin 44 may be provided. The locking hole 41 is located substantially perpendicular to the hole 42 and the circumference of hole 41 penetrates hole 42 so that introduction of locking pin 44 prevents removal of peg 43. Locking hole 41 may have any suitable cross-section such as hexagonal, square, etc. Locking pin 44 is preferably made of a hard, rigid material, e.g. metal, in particular hardened steel. The surface of pin 44 may be serrated or grooved to provide additional locking force when inserted in locking hole 41.

Sign 10 is installed in the following way. With reference to Figure 4, signage sheeting 17 is first applied to backing 16 using the adhesive layer if present. Frame 12 is then located loosely about backing member 16, signage sheeting 17 and backing plate 11 if present. Pin or pins 22 are located partially into the blind bores 25 of end joining pieces 1 8 and 20 and end joining pieces 1 8 and 20 are pushed together by hand as far as possible. Then pins 33 and 34 of tool 30 are introduced into holes 19 and 21 of end joining pieces 18 and 20 respectively. Using the considerable mechanical advantage of tool 30 the handles 31 and 32 are brought together by hand in order to exert a large closing force on end joining pieces 18 and 20 via pins 33 and 34 located in holes 19 and 2 1. This force is sufficient to drive pin or pins 22 into bores 25 of end joining pieces 18 and 20. Tool 30 is removed after the installation has been completed. Finally, a locking device may be inserted through holes 19 and 21 and locked in order to provide increased security for the sign frame 12.

Sign frame 12 may be removed for replacement of signage sheeting 17 by unlocking any locking device which has been secured through holes 19 and 20, fitting pins 33, 34 of tool 30 into holes 19 and 20 respectively and separating handles 31, 32 of tool 30 in order to pull apart end joining pieces 18 and 20.

Figure 5 is a schematic cross section of a second embodiment in accordance with the present invention. Reference numerals 51 and 52 represent an existing sign which may consist of a backing 51 and signage sheeting 52 forming an existing sign face or may consist of any of the known types of signs. In order to avoid demounting the sign, a kit in accordance with the present invention may be used. The kit includes a pre- formed or formable profile 12 similar to the profile 12 described with respect to the first embodiment. Profile 12 has one channel section 9 and an optional channel section 8 and the two end joining pieces 18 and 20 as shown in Figures 3 and 6. The width of channel 9 is selected so that channel 9 may receive at least the old sign face 52 and preferably the sign face 52 and the old backing 51 as well as new signage material 17. Optionally, a backing member 16 may be provided between signage sheeting 17 and the front surface 52 of the old sign. Backing member 16 is preferably thermally insulating and/or elastically compressible. The width of channel 9 may be selected so that it is equal to, or slightly smaller than the complete width of the old sign 51, 52, any backing material 16 provided, and signage sheeting 17. When the width of channel 9 is chosen to be slightly smaller than the combined widths of the old sign 51, 52, signage sheeting 17 and optional backing member 16 it is preferred if backing member 16 is elastically compressible. The interference fit between the old sign 51, 52, signage sheeting 17 and optional backing member 16 may provide environmental sealing for any cut edges of elements 51, 52, 16 and 17 and will protect these edges from high pressure water jets used for cleaning the signs. It is advantageous if the ends 14", 15" of the walls 14, 15 of channel 9 of the frame 12 are sloped, tapered, graded or rounded to allow introduction of the signage sheeting 17 and the backing member 16, if present, into the channel 9 without damage.

Figures 9 and 10 are schematic representations showing the installation of a replacement sign kit in accordance with the second embodiment of the present invention. An existing sign includes a sign post 50 and a sign 51, 52 attached thereto by means of a fixing device 53, 54 which may be bolts or straps 53 and tightening devices 54 which may be nuts or one of many strap closing devices. The sign is made up of a worn reflective material 52 and a backing plate 5 1. The front surface of the reflective material 52 often has heads 55 of bolts, or rivets which protrude. It is often not possible to release the sign holding means 53, 54, 55 because it is corroded, e.g. rusted.

The replacement kit may contain a backing member 16, a piece of signage sheeting 17, a pre-formed or formable frame 12 with end joining pieces 18, 19 with one or more pins 22 or end joining pieces 48, 49, and optionally an additional locking device 56. The signage sheeting 17 may be fixed to the backing member 16 by means of adhesive which may be pre-applied. The combined structure is then placed against the old signage material 52. Advantageously, the backing member is compressible or elastically compressible so that it can absorb the protruding heads 55 without significant distortion of the signage sheeting 17.

Frame 12 is then placed around the complete assembly as best shown in Figure 10. The end joining pieces 18, 19 or 48, 49 are brought together and the pins 22 or 43 are located in their respective holes 25, 42 and the end joining pieces 18, 19, 48, and 49 are forced together with the tool described with reference to Figure 7. For additional protection, a locking device 56 may be threaded through holes 19, 20 and closed.

Claims

I claim:

1. A kit for mounting a sign comprising: (a) flexible sign sheeting; (b) a length of pre-formed or formable profiled material, said profiled material having a first and a second end, said profiled material including:

(i) at least one longitudinal channel portion to receive edge portions of said sign sheeting; and

(ii) first and second complementary joining pieces adjacent said first and second ends, respectively; and

(c) a tamper-proof clamping device for clamping together a pair of complementary first and second joining pieces.

2. A kit according to claim 1, further comprising a backing member, said at least one longitudinal channel portion being adapted to receive said backing member.

3. A kit according to claim 1, respectively, wherein each of said first and second joining pieces has a first bore hole; and said tamper-proof clamping device includes at least one elongate member, said elongate member being a pass-fit in said first bore holes of said first and second joining pieces.

4. A kit according to claim 3, wherein said first bore holes are parallel to said channel portion.

5. A kit according to claim 4, wherein said first and second joining pieces each have a second bore hole.

6. A kit according to claim 1, further comprising a locking device.

7. A kit according to claim 6, wherein said locking device includes a second elongate member for introduction through said second bore holes.

8. A kit according to claim 2 wherein said backing member includes at least one of a rigid material, a compressibly deformable material, an elastically deformable material, and a thermally insulating material.

9. A kit according to claim 1, wherein said frame is square, hexagonal, round, triangular, or oblong in shape.

10. A refurbished sign including an existing sign having an existing sign face, said refurbished sign comprising: (a) a flexible sign sheeting covering said existing sign face;

(b) a length of profiled material, said profiled material having a first and a second end, said profiled material including:

(i) at least one longitudinal channel portion receiving edge portions of said sign sheeting and at least said existing sign face; and (ii) first and second complementary joining pieces adjacent said first and second ends, respectively; and

(c) a tamper-proof clamping device clamping together a pair of complementary first and second joining pieces.