PURPOSE: To make a nail hard to be pulled off and to prevent the nail from unfastening and to provide a strength against an impact by a method wherein blades are attached to a nail and protrusions are formed from the central part of the nail to which the blades are attached.

CONSTITUTION: Blades 1 are attached to a nail and protrusions 2 are formed from the central part of the nail to which the blades are attached. By attaching the blades 1 to the nail, friction is increased and by forming the protrusions 2 from the central part of the nail 1, the nail is hardly pulled off, and prevented from unfastening. Further, by attaching the blades 1, a high strength against all impacts is provided. Thus, the substantial effect of joining is produced and even when a nail is erroneously driven, the nail is prevented from bending.