An intermodal container is a large standardized shipping container, designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport – from ship to rail to truck – without unloading and reloading their cargo. Corrugating the sheet metal used for the sides and roof contributes significantly to the container’s rigidity and stacking strength, just like in corrugated iron or in cardboard boxes. Smaller 20’ international containers have castings with openings for twistlock fasteners 20’ apart on the eight corners, to allow gripping the box from above, below, or the side, and they can be stacked up to ten units high for storage.