to form the frame of a builtup type parking area. Floor materials 27 and 27 in a U-shape in cross section are joined together through a hook part by means of a joint member, the floor materials 27 and 27 are orderly intercoupled to form an upper layer parking space on the horizontal...
The peripheral wall 3 is formed in such a manner as to have an inverted U-shaped section comprising an inner peripheral wall 31 and an outer peripheral wall 32, which is raised from the bottom wall 2 and folded back at the upper end area to be extended to the lower end area. A step...