Once the lock button on the swing is pressed, this cuts off air to one side of each riders restraint. Each harness has main pawls which is the clicking you hear when the harness comes down to each riders body. There are also pawls that have one closed setting for the lap bar, as you hear when the lap bar comes over the rider's body. After the lap bar is down and the harness is down to the desired height, the operator will "lock" the harnesses. This cuts off the rest of the air to the swing, locking the anti crush pawls, which prevents the harness from going up or down during the ride cycle, until the switch is turned back to open.