Vinten Vision Pozi-Loc 3880-3 Operator's Manual page 17

With the knob still in Position 2, slide the leg in and out and gradually tighten the grubscrew
(24) until the clamp begins to grip.
Back off the grubscrew (24) by a quarter-turn (90°).
Secure the clamp knob (26) with the washer (27) and retaining screw (28). Refit the knob
cap (29).
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