PURPOSE: To produce a various shapes and sizes of wall surfaces at a low cost by installing panel members in an intermediate section of the wall surface and, at the same time, cutting off corner members in accordance with width measurements of an installation place to control the full width measurements of the wall surface.

CONSTITUTION: Plate-like panel members 10 are installed in an intermediate section of a building 1, basic end side corner members 20 bent in 135 are provided to the end of the basic end side of the building of the panel members 10, and tip end side corner members 30 bent in 90° are provided to the end of the tip end side of the building of the panel members 10 to form a built-up wall surface 3 of a balcony 2. After that, when basic end side measurements A of the balcony 2 have different measurements such as A1, A2, and A3, side measurements B between the corner members 20 and 30 also have different measurements such as B1, B2 and B3. Then, basic end side corner members 21, 22 and 23 adjusting width measurements of the panel member 10 to different measurements such as C1, C2 and C3 are used.