To ensure certain holding by enlarging the rear region of an expansion wedge than the outside profile of a flange-like operation part, and holding the expansion wedge by pressing and engaging it with a through hole of the operation part in an expansion state of the expansion wedge.

An expansion wedge 2 of an attachment assembly is provided with a projection 15 radially projecting at a trailing end section 14 projecting from a flange-like engagement part 5. The projection 15 is formed in a nose shape projecting from the side surface profile with crimp of material of the expansion wedge 2, and is constituted so as to press and hold the expansion wedge 2 in the expansion state in a through hole 3. Using expansion of the attachment assembly in a storing hole 13, a hitting tool is hit until a rear end 8 is on the same plane as the front surface of the operation part 5 of the trailing end 6 of an anchor bolt 1. For ensuring the hitting, the expansion wedge 2 is provided with a cut region 12, so that the trailing the section 14 of the expansion wedge 2 follows the hitting direction in a hitting work even for hard storing material 10. Thus, the attachment assembly can hold the expansion wedge at a prescribed position.