| 摘要 |
[Problem] The present invention improves freedom of assembly. [Solution] The present invention has: a main body, which has a rectangular parallelepiped shape in which one or multiple unit size cubes represented by 1 x 1 x 1 when 1 is defined as the unit side length (D1) are joined together, has a surface that is open for the bottom face, and is configured from four side walls (3B) and an upper surface (3A); and a cylindrical projection, which has a cylindrical shape, is provided on the exterior of one or more of the upper surface (3A) and the side walls (3B), and has a diameter (D2) of 0.4 to less than 0.6 times the unit side length (D1) and a height of (1-diameter) x (0.4 to 0.5). |
