A plurality of pin legs descends from a pin flange, pin leg through holes and pin acceptance cavities are formed in a bushing flange and bushing leg, leg spreaders are formed in the tip ends of the bushing leg, first locks are formed in the tip ends of the pin legs, for latching on permanent fastening projections of the leg spreaders so as to maintain the pin legs that have been diametrically spread by the leg spreaders in a permanently coupled condition, and second locks are formed at positions different from those of the first locks, for latching on temporary fastening projections in the bushing leg, whereupon the pin leg through holes restrain the diametrical spreading of the pin legs in the radial direction so that the tip ends of the pin legs can be inserted into the attachment holes of the members being attached to.