A method of manufacturing an optical element comprises testing an optical surface of the optical element, using an interferometer 1a directing measuring light onto the optical surface wherein the measuring light traverses two successive holograms disposed in the beam path of the measuring light upstream of the optical surface. The beam may include a pair of plates that are close together when the beam is in a collapsed condition, and separate from one another to put the beam in an expanded condition. According to the invention, the fastening means has a U-shaped bend, which runs in a second plane that is perpendicular to the first plane. Each of the first and the second bag provides attachment structures for attaching front pouches, side pouches and cold-drink pouches. The connection portion of the first pulley is connected to the first dial knob and the gear portion of the second pulley is meshed with the gear in a state that the pulley unit is attached to the body.