PURPOSE: To prevent destruction of a driving layer by bending outward each end of a wire in inverted U form.

CONSTITUTION: A rod-shaped anchor member 4 is interposed between the bottom of a shaft 2 and over a crest part 1d, wherein the bottom of the anchor member 4 confronts a hole 1c provided in an outer cylinder 1. The anchor member 4 is made from a round metal wire of steel and bent in inverted U form, and the ends 4a of the metal wire are laid down and bent as confronting the inside of the hole 1c. When the head 2b of the shaft 2 is driven by hammer, the outer cylinder 1 and shaft 2 are consolidated by a spacer 6, and the outer cylinder 1 is driven till a flange 1b to stop there. With another strike, the outer cylinder 1 is stopped moving by the flange 1b and compressed by the head of the shaft 2, and the spacer cylinder 6 is split and segregated. With a subsequent strike, attachment of adhesive 3 is released, and the shaft head 2b is driven to the surface of the flange 1b. At this time, the anchor member 4 emerges out of the hole 1c and intrudes into the underlay layer B without destruction of the layer, and thus anchor is achieved.