A system for loading cargo containers and flat racks off of a truck having a hook lift system onto a trailer and from the trailer back onto the truck comprising a carriage that is moveable along a track system that runs the length of the trailer. The carriage includes a cradle that a cross member located at the lower rear edge of the container on which it fits so that the carriage supports the rear portion of the container as it travels rearwardly along the trailer. The cradle includes side positioning blocks which center the container on the trailer as it is being placed in the cradle. Also located on the carriage is a receptacle which receives wheels located at the lower rear edge of flat racks. A carriage return mechanism urges the carriage forwardly as it approaches the front of the trailer. Locks at the front and rear of the trailer secure the container to the trailer.