PURPOSE: To enable simple construction to be performed even by an unskilled person and at low cost, by providing suction depressed parts to the bottom surface of a sheet material formed by welding re-vulcanized chip shaped crushed waste tire rubber materials leaving gaps for fuse bonding.

CONSTITUTION: Waste tire rubber are cut and crushed into chips and pellets and rubber crushed lumps 1, 1,... of these chips and pellets are subjected to re-vulcanization treatment to obtain a covering material (a). In this case, molding is performed so as to preperly leave buffer gaps 2, 2,... between the crushed lumps 1, 1,.... By this method, the crushed lumps 1, 1,... develop own elastic functions while spanning the gaps 2, 2,... and the damage of the elastic function of each lump accompanied by re-vulcanization is effectively compensated. Subsequently, depressed parts 3 to be sucked to a surface to be contacted one provided to the bottom surface of the covering material (a) while the gaps 2 in the crushed lumps 1 are sealed so as to hermetically suck the depressed parts 3 by the surface to be contacted and formed into a smooth end surface so as to certainly and uniformly contact with the surfaces to be contacted of the depressed parts 3.