A bow sight having a support member with a sight unit disposed at one end and adjustable sight markers secured to the other end, a pointer associated with the rear end of the support member for alignment with one of the sight markers upon determination of the proper sight unit elevation setting. In practice, the stage comprises two identically sized platform surfaces, the lower surface or deck rests on ground engaging wheels and includes steering, brake and tow bar mechanisms to facilitate the movement of the stage. Each first U-shaped strip portion has two ends connected fixedly to the intermediate plate, and a bent portion connected fixedly to the inner wall. The flanges are disposed at axial edges of the metal member in contact with an inner circumferential surface of the metal member. The tooth length in both sections is dimensioned in such a way that in neutral position, the input shaft can rotate while the toothed wheel remains stationary but is prevented from rotating while the input shaft remains stationary. The optical element according to the invention overcomes the problem of wrinkling foils by creating an underpressure that presses the foil against the rigid plate, thereby preventing the foil from wrinkling.