PURPOSE: To make driven leg parts to slip of hardly by providing groove parts which are crossed at right angles to driving direction on the way of the outer or inner side surface of at least one of leg rods, in a nail which is constituted by a straight connecting rod and leg parts which are continued in parallel from the both ends of the connecting rod.

CONSTITUTION: A nail A is composed of the straight connecting rod 1 and a pair of leg rod 2 which are continued in parallel from both ends of the connecting rod 1, and groove parts 3 which are crossed at right angles to driving direction are provided on either one of the outer side surface or inner side surface of at least one of the leg rods 2. For example, water proof sheet 12 is piled on the surface of a foamed concrete plate 11, and the nail A is driven from the surface thereof toward the foamed concrete plate 11. The leg rod 2 is bent in an arc shape between the groove part 3 and a driving top end by the groove part 3. The leg rod 2 is bent widely outward since the groove part 3 is provided on the outer side surface of the leg rod 2. It is thus possible to make the leg part of the nail A to slip off hardly, increase supporting force of the leg rod 2, and maintain stable supporting force.