PURPOSE: To surely and easily fit an external wall member to a bed without allowing the head of fixtures to come out on the decorative surface of the wall member by fitting the wall member to the bed by tightening fixtures passed through holes formed through the rear of the external wall member only and fitting holes formed through the bed at once.

CONSTITUTION: This external wall member 1 is constituted of a decorative surface 2, rear 3, through holes 3a, side walls, and partitioning internal walls and the side walls are formed to a male or female structure depending upon their aimed use. Fixtures 6 are united with the rear 3 of the wall member 1 at once in such a way that the fixtures 6 are passed through the holes 3a and expanded outward on the surface 3b of the rear 3. After the rear 3 of the member 1 thus prepared is put on a base 7, with the through holes 3a being aligned with the fitting holes 8 of the bed 7, and the fixtures 6 are passed through the holes 8 these are tightened at once.