To prevent a falling accident and reduce the labor of works by safely conducting all works easily from a room in an upper floor in the case of the maintenance works of a cabinet formed on a wall surface.

An opening section 2, having height of approximately 600 mm and the same width as a niche N, is formed at the lower end of a wall body 1 installed between the niche N formed by indenting the wall surface 1 of a living room L and the room R in the second floor, four removable walls 3 are inserted normally into the opening section 2 and the opening section 2 is previously closed completely, and the necessary removable wall 2 is removed from the room R side of the second floor, and a hand is stretched and works are conducted in the maintenance of the niche N.