The first fixing member and the second fixing member are arranged such that the first clamping surface and the second clamping surface face each other in an axis line direction of the insertion portion. When the manipulation portion is manipulated and the insertion portion and manipulation member is rotated relatively, the first clamping surface and the second clamping surface are configured to approach by screw-fitting with the second fixing member and the first fixing member. When a predetermined manipulation is performed to the manipulation portion, a coupling between the manipulation member and the other is configured to be released.