Rack 1 has rectangular teeth d and slides in fixed guide a. Reversible pawl 2 can be turned about fixed axis A and engages teeth d of rack 1. Pawl 2 may be turned to the position shown by dash lines. In the first position the pawl allows rack motion only to the right; in the second position - only to the left. The pawl is held in engagement with the rack in either position by gravity.
$2682$RG,3L$