A pair of elongated latches positioned transversely to a longitudinal axis of a railroad car particularly adapted to be rotated to an upside down position for gravity release of contents within the car, are pivotally attached respectively on each side of a top of a coupler lock. The coupler lock is an operative part of a coupler for the railroad car. The lock is movable within a lock chamber formed in a head of the coupler and is defined in part by vertical sidewalls and a roof or top wall. A configuration of each latch and relative position to the lock chamber sidewalls is such that a center of gravity of each latch lies above its pivot connection which insures that regardless of the direction of rotation of the car, at least one of the latches readily swings to an extended position to engage the top wall of the lock chamber and thereby prevent an inadvertent release of the lock when the car and at least one pair of mated couplers are rotated toward an inverted position for emptying contents of the car.