To provide a form having large strength at a low cost by overlappingly connecting the end sections of batter materials, and fixing the connection sections via multiple fastening washers for reinforcing the back face of a sheathing board l connected with metal forms with the batter materials.

Frame plates 4 (flange sections) of rectangular metal forms 2 having reinforcing ribs 5 are connected together by bolts and nuts 7 to form a sheathing board 1 having the required size. The sheathing board 1 is assembled on the ground, and multiple batter unit materials 9 are arranged on its back face at intervals in the direction perpendicular to the rectangular metal forms 2. The connection sections of the batter unit materials 9 are overlapped in parallel, and they are fastened to the reinforcing ribs 5 or the frame plates 4 (flange sections) by fastening bolts 10 via fastening washers 15. The sheathing board 1 is conveyed to the required place by a crane or the like, and it is assembled as a concrete form. The structure of the whole form is simplified, it is made lightweight, and the execution efficiency can be improved.