A deck attachment fitting, a deck socket and a socket and attachment assembly for use particularly to position and hold down standard freight or shipping containers having standard corner fittings on the deck of a ship or other carrier. When used as an assembly, the socket is welded to the deck and the attachment fitting may for example be a stacker key to fit in a corner fitting, or a device for securing the end of a cable. The deck socket includes a body member having a circular series of undercut arcuate lugs, and the attachment fitting is provided with a similar but oppositely configured projecting series of such lugs. The two parts are engaged with one another by placing them in face-to-face relation and by inserting the lugs of the fitting between those of the deck socket and rotating the fitting through a predetermined angle which depends upon the number of lugs. Corresponding lugs have mating surfaces which engage one another and provide a broad surface to broad surface tight fitting contact having high load-bearing capability. A deck socket or attachment fitting having chain link receiving sockets may be used individually for lashing.