Abstract: A cargo container is provided with a door opening having means for engaging and disengaging the top and/or bottom of the door on vertical movement thereof. A hollow rail extends across the top and/or bottom of the door opening and has elongated slots therein provided with slot-enlargements for receiving a foot or feet of a locking member movable along the bottom and/or top of the door. The locking member includes a reduced portion movable through the slot and an enlarged portion having a transverse dimension greater than the width of the slot. Suitable means, preferably rack and pinion means, are provided for shifting the locking members along the door to locking position after movement through the slot-enlargements into the interior of the rail.