Skeleton unit and skeleton unit assembly

A skeleton unit to mount a plurality of mosaic cover plates, comprising:

• a main body section, which is integrally formed by a plurality of strip pieces perpendicularly crossing each other to present a grille shape, comprising a plurality of grids with a size and a shape corresponding to the mosaic cover plates;
• an extension section, which extends out from four edges of the main body section and is integrally formed with the main body section, the extension section comprises a plurality of prolongation pieces which respectively extend out from both ends of each strip piece, and a plurality of parallel strips which connect with outside ends of each prolongation piece on a same side and are in parallel with the edges of the main body section, respectively;
• wherein a length of a parallel strip is equal to a length of a strip piece, a height of the parallel strip is less than half a height of the strip piece;
• wherein first two adjacent parallel strips are in an alignment with a bottom surface of the main body section, and top parts of second two adjacent parallel strips are fixed at positions close to a top surface of the main body section;
• wherein the parallel strip is provided with a plurality of lap joint hole portions penetrating the parallel strips and are used to overlap another skeleton unit;
• and
• wherein a sum of twice a length of a prolongation piece and a width of the parallel strip is equal to a length of a grid.