To always apply the turning force so as to follow up the change with time of a material to be fastened by providing a spring working on the bolt head part to energize the fastening direction and a hexagonal hollow shaft in the interior of an inner cage fixed to a flat plate.

A circular hole is bored in the central area of a flat plate 4, a double conical shape of an inner cage 3 is fixed to the flat plate 4, a spring 5 is fitted to the inner cage 3, and the spring 5 is also connected to a hexagonal hollow conical shaft 2. Further, a conical outer cage 1 slotted to be circular is put thereon, and a screw 6 is fastened to the inner cage 3. Secondly, with the assembled flat plate 4 fitted to the bolt head and turned in the rotating direction of fastening the bolt, hardware is fixed by a nail or screw. Thus, in the structural connecting part of a wooden dwelling house, the bolt is turned following up loosening of fastening caused by shrinkage of wood connected by the bolt so that fastening is automatically advanced.