Abstract: A sea-land shipping container slideout conversion system, where the slideout unit generally has a floor, three walls and a roof. The slideout is mounted on a pair of vertically parallel slidable elevation members, which are slidably attached to two parallel horizontal sliding rails. The side of the container is cut out for the slideout and a ridged steel frame is welded into the cut-out. The slide rails slide in four spaced-apart roller box units that are mounted under the container between the container floor joists. The slideout unit is balanced and raised on the elevation members and slid inside of the container on the slidable rails. A plurality of seals are added to the slideout unit to seal the slideout unit to the container, both when the slideout unit is retracted and extended. When slid out of the container and lowered the slideout is locked in place outside of the container, so the floor of the slideout unit is level with the floor of the container and effectively sealed with the container.