PROBLEM TO BE SOLVED: To provide a clasp which constitutes necessary functions for a collar, a harness, and a lead (a leash) with simple parts when being applied for example to equipment for animals, and can achieve the collar, the harness, and the lead (the leash) which are lightweight and impose a less burden on a pet by eliminating the number of unnecessary parts.SOLUTION: A clasp includes a connecting pin which is inserted in an insertion hole of a member having the insertion hole and a ring-shaped member which has a diameter part that is larger than an inner diameter of the insertion hole and keeps an insertion state of the connecting pin. The connecting pin has a protruded part to be inserted in the insertion hole and a flange part having an outer diameter larger than the inner diameter of the insertion hole. The ring-shaped keeping member is inserted in a through-hole provided on the protruded part to keep the inserted state of the connecting pin in the insertion hole.【課題】例えば動物用装具に適用した場合、シンプルなパーツで首輪胴輪とリード（引き綱）の必要機能を構成でき、不要なパーツ点数を省くことで、軽量でペットへの負担が少ない首輪胴輪、リード（引き綱）を実現可能とする留め具を提供する。【解決手段】留め具は、挿入孔が形成された部材の前記挿入孔に挿入する連結ピンと、前記挿入孔の内径より大きい径部分を有しかつ前記連結ピンの挿入状態を保持するリング状部材とを備え、前記連結ピンは、前記挿入孔に挿入される凸部と挿入孔の内径より大きい外径を有するフランジ部とを有し、前記凸部に設けられた貫通孔に、前記リング状保持部材が挿入され、前記連結ピンの前記挿入孔への挿入状態が保持されることを特徴とする。【選択図】図１
