Provided is a stay which is capable of stabilizing movement of a component part used for transmitting, or not transmitting, the torque of one of a first member and a second member to the other. When a second member rotates relative to a first member in one direction, a cam base moves away from a disk in the direction of the rotation axis, and the second member and the cam base rotate relative to the first member and the disk. When the second member rotates relative to the first member in the opposite direction, the cam base moves towards the disk in the direction of the rotation axis, and the second member, the cam base and disk rotate relative to the first member with resistance force.