In combination: a) a chassis with a first frame and a first twist lock assembly, with an enlarged head, on the first frame; and b) a cargo carrying container mounted in an operative position upon the chassis. The cargo carrying container has a second frame and a second twist lock assembly on the second frame that cooperates with the first twist lock assembly. The second twist lock assembly has a slide plate with an aperture through which the enlarged head is passed in an axial direction with the enlarged head in an assembly/disassembly orientation. The enlarged head in the assembly/disassembly orientation, moving relative to the slide plate in the first axial direction, deflects the slide plate from a first position to allow the enlarged head to pass through the slide plate aperture.