To provide an open leg nail and its driving method without causing a driving failure, also an installation method and an installation structure of a member fixing bracket by using the nail and the method.

This open leg nail A is composed of a first nail body 1 for arranging an open leg control part 3 for opening the tip of a second nail body 2 at a tip part and the second nail body 2 for opening the tip by being constituted separately from the nail body 1, and characterized in that a shaft 1c of the nail body 1 and a shaft 2c of the nail body 2 are fitted in parallel in a pipe 4 in a state of arranging a head 2b of the nail body 2 on its outside of a head 1b of the nail body 1 on the head 1b side of the open leg control part 3 for arranging a tip part 2a of the nail body 2 in a tip part 1a of the nail body 1, and are slidably restricted in the axial direction by the pipe 4.