PURPOSE: To facilitate the removal of a rubber root after placing concrete, and to prevent the peeling of a mortar by arranging the rubber root which is tapered on the outer surface, on the inside of a sheathing, and by forming a separator which penetrates the rubber root, in such a way that a notch can be provided, on the position of a small diametral part.

CONSTITUTION: A tapered rubber root 1, which is opened in the rear part on the outer surface, and which is to be solidly molded out of a rubber elastic body, is arranged on the inside of a sheathing 8. A separator 9 that penetrates a cylindrical part, is formed on the position of a small diametral part 9b of a part that is in contact with a bottom 2 of the rubber concrete 1, in such a way that a notch can be formed. A cap nut 11 is engaged with the end of the separator 9 protruded to the surface, through a screw, while a concrete 17 is placed in the sheathing 8 supported from an inner pressure by a bolt 12 which is integrated into the cap nut 11, a bracket 13, and by a nut 14, and after the concrete is hardened, a finger hook hole 5 of a tongue piece 4 for finger hook of the rubber root 1, is pulled by finger, and is thus removed, along with various members, and the end of the separator 9 is notched by the small diametral part 9b, so as to construct a mortar 21, and a tile 22. The peeling of the mortar can thus be prevented.