PURPOSE: To provide the titled member which has high durability, is usable for a part to be applied with external force and has simple construction and to improve productivity by constituting the member in such a manner that the part thereof to contact the slide guides of a stationary barrel and the part to contact the screw threads of a distance ring slide by making face-to-face contact.

CONSTITUTION: The guide pieces 1... fixed to a lens barrel 5 tend to rotate according to the rotation of the distance ring 7 when said ring rotates. However, the guide pieces cannot rotate as said pieces are limited by guide slits 61... of the stationary barrel 6; therefore, the guide pieces are moved forward and backward along the guide slits 61... by the component of force generated in the forward and backward directions by a lead angle α. namely, the guide pieces 1... act both as external screws of rectilinear helicoids and guide plates. As a result, the lens barrel 5 moves forward and backward when the ring 7 is rotated. Deformation is thereby prevented; in addition wear loss by friction is decreased and the durability is improved. The number of parts is thereby decreased and the assembly operation of a lens body is simplified.