If stops or other stroke limiting elements are subject to direct pressure or impact, the security of their positions must be accomplished by positive, nonfrictional engagement of parts, and they must be adjustable to provide for deliveries within prescribed tolerances. If two or more stops or other elements may selectively be brought into operation to permit deliveries or predetermined amount, the position for the proper setting of each of such elements must be accurately defined, inadvertent displacement from position must be obstructed, and the delivery for which the device is set at any time must be conspicuously indicated.
Okla. Admin. Code § 165:15-15-44