The invention relates to a fastener (10) for the temporary joining of at least two pre-pierced structures, of the type comprising: - a body (11) that is liable to come into contact with a face of the structures to be joined, - a spacer (17) secured to said body, - two elastic half-grippers (15), each gripper being provided with a catching spur (16); - a mechanism that is movable with respect to the body, comprising a threaded rod (18) connected to the half-grippers and a drive nut (20) mounted on said rod, the drive nut comprising: - an internal thread (19) that engages with the thread (25) on the rod, - an external thread (26) that engages with an internal thread (28) on the body, the thread on the body and the thread on the drive nut being of opposite hand.