PURPOSE: To safely and easily carry out an assembling work in a building.

CONSTITUTION: Plaster board 5A, 5B are applied to the opposite surfaces of a core material 2 before the latter is fixed in a building 11 with a high degree of efficiency. Even though it is fixed in the building, the upper and lower end edge parts 3A, 3B, 4A, 4B of the core material 2 are not applied thereon with the plaster board 5A, 5B, but are driven thereinto with pegs 14. The heads of the pegs 14 may be concealed, and the upper and lower end parts of cloths 6A, 6B may be processed.