Abstract: A safety cage hoisted atop a stack of interlockable cargo containers provides safe access to the locks. The dimensions of the cage are substantially identical to the dimensions of the containers. Eyes in the upper corners of the cage frame are engaged by the container bridle hooks. Hinged deck plates in the corners of the cage open to provide access to the locks immediately below. A reeled tether hanging from a trolley which rolls along the athwartship extension arms of a roof boom hooks onto a worker's safety harness to enable him to leave the cage and reach remote locks in safety. The boom rotates between stowed and deployed positions and is held in place by quick release catches. A spring actuated pin engages a tapered hole to lock the extension arms in place. Baskets disposed along the perimeter of the cage are used for storing the locking cones.