A readily attachable and detachable firearm attachment for mounting firearm accessories to a firearm forearm rail is provided by an attachment having a pair of rail clamping and locking jaws. At least one of the jaws is a movable jaw actuated by a levered cam equipped with a locking system to lock and anchor the attachment to the firearm rail and a quick release for unlocking the cam to permit a release of the jaws from the rail.