Abstract: A QCD coupling in which a rotating subsidiary locking means is provided which is both positive in its locking action, locks all of the levers simultaneously, and does not involve any small or readily losable parts, as the subsidiary locking means is itself securely attached to the coupler part of the QCD coupling. As all of the levers are locked simultaneously, the subsidiary locking means cannot be locked unless all of the levers are in the fully “locked” position.