To fix a nail in the same way as a screw only by driving the nail by forming a specific number of leg tips.

A nail 1 is perceived with two tips. This nail 1 is driven by boring two holes in the light ceiling. Then, a distance between two points of the holes bored in the light ceiling does not change, and since a branched part of the nail 1 gradually narrows in a Y shape, the leg part expands at a obtuse angle. Legs largely open as this branched part approaches the light ceiling. Thus, it can be made nonextractable by expanding the leg part to an obtuse angle only by driving force by forming the leg part on the tip of the nail 1 into two pieces. A construction period of light ceiling work can be largely shortened by executing this nail 1 by a nailing machine.