Quick-release base replaces OConnor Mitchell base & tie-down. It eliminates the separate tie-down knob that must be threaded into the bottom of the head each time the head is mounted. Instead, the Cardellini Head-Lock is part of the base plate and stays on the bottom of the head. When the head is placed on the dolly, tri-pod, etc., the Head-Lock passes through the center of the Mitchell Mount. Turning the built in knob from below extends three angled jaws that lock the head in place.