PURPOSE: To save manpower for the execution of work and prevent the generation of unevenness on a floor.

CONSTITUTION: A ground sill 1 which supports wall 8 is fixed to the top of a foundation 3. A presser 6 is installed to a side surface of the ground sill 1 while an insertion part 4 is installed to the end of a horizontal frame material 5. The insertion part 4 is inserted between the top of the foundation and the presser part 6 while a wedge 7 is driven between the presser part 6 and the insertion part 4, thereby fixing the horizontal frame material 5 to the foundation 3. This construction makes it possible to mount easily the horizontal frame material 5 to the foundation 3 with the insertion part 4 and the wedge 7, thereby eliminating the need for a bundle of woods or stones. Since the horizontal frame material 5 is mounted to the foundation 3 whose height is formed definitely, it is possible to fix the height of the horizontal frame material 5.