Abstract: A base portion 122 in a hook 12 having an arc-shaped portion 121 is pivotally secured to a main body 11 by a pivot pin 15. A tip end 124 of the arc-shaped portion 121 projected outward from the main body 11 is mated with and disengaged from a mating end 13 of the main body 11. The hook 12 is urged by means of a spring 14 so that the tip end 124 is naturally mated with the mating end 13. For the attachment, the main body 11 is pinched with fingers of one hand, while the arc-shaped portion 121 is pivoted against the bias action of the spring 14 with the same hand so that the tip end 124 is separated from the mating end 13. Then, the arc-shaped portion 121 latches, from its tip end 124, the chain's end 21 pinched with the other hand. For the detachment, the end 21 is pulled so that the tip end 124 is moved outward with respect to the center of the arc-shaped area surrounded by the hook 12. Further, the end of the chain 41 is pulled so as to reach the tip end 124, thereby the end of the chain 41 is detached.