To block a separator bolt hole certainly by inserting a mounting part in the separator bolt hole provided in a concrete surface, and fitting its internal threads on a separator bolt which protrudes from the hole.

The body 12 of a mounting part has an outside diameter some smaller than a separator bolt hole 31 in a part on the concrete surface 30 which is to be inserted into the separator bolt hole 31 and is shaped approx. cylindrically as thinning toward the bottom surface of the hole. An air bleeding groove is provided in the cylindrical direction at the outside circumferential surface of the mounting part 11, and the air in the hole 31 is released to the outside to ensure eventual operation that the gap between the hole 31 and mounting part 11 is filled with a sealant, etc. This decoration piece 10 is certainly attached only by fitting the internal threads of a threaded member on the separator bolt 32 which is protruding to the hole 31 so that the separator bolt can be blocked, and the bolt hole and its peripheral edge are hidden with fine workmanship.