Entanglement of bush main bodies is suppressed. At a bush, a shaft portion of a bush main body, which extends in a circumferential direction of a mounting hole of an outer anchor, covers a peripheral surface of the mounting hole. A first flange portion and a second flange portion of the bush main body are placed on an front and back sides of the outer anchor, respectively. Moreover, a connection portion connects both circumferential direction sides of the bush main body. The connection portion allows elastic deformation of a diameter of the bush main body, and the second flange portion can pass-through the mounting hole.