PURPOSE: To make it easy to drive a nail and to engage with/disengage from a fixed object and to aim at cost reduction by constructing the nail in the caption by a nail shaft providing an expanding taper face at the top end of a groove wall and a small hole on an upper end, and a nail member having a nail shaft which screws and connects therewith.

CONSTITUTION: An expanding slot 22 is formed with leaving the upper portion of a nail shaft 2 and the nail shaft 2 is formed by forming a taper face 24 expanding the top portion of groove wall toward a top end and boring a small hole 25 on an upper portion. A nail member 3 having a base 31 the diameter of which is larger than that of a shaft portion 21 is screwed into a small hole 25 via a packing 34. Accordingly, it is easy to drive a nail 1 to fix it, and also to remove a fixed object and to exchange than, mass-production is possible and they can be manufactured at a low cost.