PURPOSE: To prevent any leakage of concrete from occurring as well as to get rid of any high pressure jet washing work by installing a cleat serving as a joint setup part in the whole circumferential part of an edge side of a platelike decorative body and also a projection on a surface of this joint setup part over the whole circumference in the almost orthogonal direction, respectively.

CONSTITUTION: A tile sheet manufacturing form cleat 4-1 serving as a locking part of a joint sealer over the whole circumference is installed in a tile sheet manufacturing form 4. Next, a joint setup surface (1)-4 of a tile cleat part (1)-3 is stuck close to a joint surface, forming a horizontal seal 10, and it is completely sealed. In addition, a projection (1)-5 is put on the joint setup part surface (1)-4. With this constitution, the joint sealer is not penetrated more than that by the form 4-1, concrete depth in an clearance is kept constant, such finishing as being good in appearance is thus achievable.