Abstract: A cover for a housing—and particularly for a swimming pool drain—is lockable by a bridge having downwardly extending upper arms and upwardly extending lower arms that are drawn towards one another by a bolt passing through threaded upper and lower hubs for the arms and having a first thread along an upper substantially one-half length thereof and a second opposing thread along a lower substantially one-half length thereof, with the bridge also having bearing feet pivotally connected between adjacent facing ends of the arms to exert increasing pressures against inside surfaces of the housing as the arms are drawn towards one another in securing a rested cover for the housing into a lock position.