PURPOSE: To quickly and safely drive a joining nail as planned by providing the nail part to act in the direction opposite to the nail, and formed into an optional shape on a head part of the optional shaped nail.

CONSTITUTION: The nail part 3 so formed as to act in the direction opposite to a nail 1 is provided on a head part 2 of the nail 1 formed into an optional shape. The nail part 3 can be inserted into a hollow part 6 of an auxiliary tool 11. When a joining nail is driven into a main stem 7, the nail part 3 is covered with the hollow part 6 of the auxiliary tool 11, and the upper surface 13 of the auxiliary tool is hammered by a hammer 12, so as to be used. The joining nail can be accurately and quickly driven to the planned depth even by an unskilled person by using the joining nail and the auxiliary tool, and it can be safely driven without hammering the side of the nail part 3 and without hammering his finger.