Abstract: A container chassis is supported at one end by a movable bogie unit or "slider" mounted below it, and has a sliding bolster unit mounted above it to accommodate a heavy twenty foot cargo container. Retractable roller mechanisms on the bogie unit and on the bolster unit are urged against the chassis to permit easy placement of a unit at a desired position along the chassis, and a releasable coupling between the slider and the bolster allows the bolster to be moved along the chassis by the slider. Protocols are described for moving a container between a first position centered on the chassis and a second position flush with the rear of the chassis. In a preferred embodiment, the front portion of the chassis is elevated with respect to the rear portion, so that the bolster slides along a region lower than the front. With the bolster in its rearmost position, the chassis accommodates a forty foot container.