A STRUCTURE FOR ASSEMBLAGE 1. Field of the Invention The present invention relates to a structure, especially to a structure for assemblage. 2. Description of the Related Art 5 There is a structure for fastening frames of parts in fields such as the solar power engineering or the battery case. Inventors of this field endeavor to facilitate the assemblage of the structure and fasteners thereof with a swift and stable fixing of ended products. SUMMARY OF THE INVENTION The main object of the present invention is to provide a structure for assemblage that is able 0 to stabilize connecting and fixing as well as facilitate disassemblage. The present invention is achieved as follows: a structure for assemblage comprises a structure, a fastener, and a connector. Characterized in that, the structure includes two slots that are generally shaped into a U-shape thereon, and the structure also includes a groove. Every slot has an opening defined at a top part thereof. Two edges are symmetrically formed on an inner 5 part of each opening. A top of the groove is an open hole, and a curved slot is respectively defined on two sided walls of the groove. The fastener is consisted of a block and a threaded bolt for cooperating with the slot of the structure. The block is formed into an inverted trapezoid shape of which an upper part is larger than a lower part. A middle part of the block defines a threaded hole for a threaded bolt to penetrate, an up part of the block defines an indentation for 20 cooperating with the edge of the slot, and a down part of the block is formed into a curved surface that is gradually diminished. The connector is cooperated with the groove of the structure. Two sides of the connector are outward extended for forming protrudent parts. The protrudent parts are adaptively engaged with the curved slot of the groove. An aperture is defined on the connector. 1 Preferably, two ramps are symmetrically arranged on the up part of the block of the fastener. Preferably, the fastener includes an engaging element disposed on the opening on the top part of the slot of the structure; wave lines are formed on an inner surface of the engaging 5 element; a middle section of the engaging element provides a through hole for the threaded bolt to penetrate. Preferably, a strengthening rib is disposed on a bottom part of the slot of the structure. Accordingly, the present invention achieves effects as follows: 1. The block of the fastener directly gets into the slot of the structure at a desirable position. 0 Fastening the threaded bolt is able to fix the assemblage. Thereby, the assemblage of the structure and the fastener is swift, and the working efficiency is also enhanced. 2. While the protrudent part of the connector and the curved slot of the groove are adaptively engaged, the connector and the groove are able to move horizontally and vertically, so that the assembled structure is more stable. 5 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of the present invention; Fig. 2 is a sided view of the present invention; Fig. 3 is a rear view of the present invention; Fig. 4 is a perspective view showing a further embodiment of the present invention; 20 Fig. 5 is a sided view showing the further embodiment of the present invention; Fig. 6 is a perspective view showing a third embodiment of the present invention; and Fig. 7 is a sided view showing the third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description is depicted along with the correlated figures. 2 Referring to Figs. 1, 2, and 3, a structure for assemblage of the present invention comprises a structure 1, a fastener 2, and a connector 3. Wherein, the structure 1 includes two slots 11 that are generally shaped into a U-shape thereon, and the structure also includes a groove 12. Every slot 11 has an opening 111 defined at a top part thereof. The openings 111 of the slot 11 are 5 arranged in different directions, so that the screwing can be conducted from two different directions. Two edges 112 are symmetrically formed on an inner part of each opening 111. A top of the groove 12 is an open hole 121, and a curved slot 122 is respectively defined on two sided walls of the groove 12. The fastener 2 is consisted of a block 21 and a threaded bolt 22 for cooperating with the 0 slot 11 of the structure 1. The block 21 is formed into an inverted trapezoid shape of which an upper part is larger than a lower part. An outer diameter of the block 21 is slightly smaller than an inner diameter of the slot 11, but larger than a dimension of the opening 111. A middle part of the block 21 defines a threaded hole 211 for a threaded bolt 22 to penetrate. Two ramps 212 are symmetrically arranged on an up part of the block 21 of the fastener 2. An indentation 213 is 5 disposed below the ramps 212 for cooperating with the edge 112 of the slot 11, and a down part of the block 21 is formed into a curved surface 214 that is gradually diminished. The connector 3 is cooperated with the groove 12 of the structure 1 and fixed in the groove 12. Two sides of the connector 3 are outward extended for forming protrudent parts 31. The protrudent parts 31 are adaptively engaged with the curved slot 122 of the groove 12. An 20 aperture 32 is defined at a predetermined position on the connector 3. In assemblage, one end of the block 21 is inclined for entering the slot 11 via the opening 111. The other end of the block 21 thence enters the slot 11 via the curved surface 214 at the down part of the block 21. When the block 21 is set in a proper position, the threaded bolt 22 brings the block 21 upward, so that the indentation 213 of the block 21 is able to adaptively 3 engage with the edge 112 of the slot. As to the connector 3, the protrudent part 31 enters the groove 12 via the curved slot 122. Afterward, a screw 4 is screwed in the aperture 32 of the connector 3, so that the connector 3 is fixed in the groove 12. Thereby, the connector 3 is able to be assembled with the structure. Namely, when the protrudent part 31 of the connector 3 is 5 appropriately engaged with the curved slot 122, the connector and the groove do not randomly move in a horizontal direction or in a vertical direction. Therefore, the assembled structure is more stable. Referring to Figs. 4 and 5, a further preferred embodiment is shown. Differently, the fastener 2 includes not only the block 21 and the threaded bolt 22 but also an engaging element 0 23. The engaging element 23 is disposed on the opening 111 on the top part of the slot 11 of the structure 1. Wave lines 231 are formed on an inner surface of the engaging element 23. A middle section of the engaging element 23 provides a through hole 232 for the threaded bolt 22 to penetrate. Accordingly, screwing the threaded bolt 22 allows the block 21 and the engaging element 23 to be fixed to the structure 1 in an upper-lower relationship. 5 Referring to Figs. 6 and 7, a third preferred embodiment of the present invention is shown. Herein, a strengthening rib 13 is disposed on a bottom part of the slot 11 of the structure 1. Whereby, the strengthening rib 13 is able to prevent the U-shaped slot from deforming, enhance a supporting force of the bottom part of the slot, and promote a fastening effect of the fastener. 4