The CONEX box, a portmanteau of "Container, express", is a type of cargo container that was developed during the Korean War and was used to transport and store supplies during the Korean and Vietnam w
A mix of modern standard containers and old Conex boxes used for training purposes, Fort Carson, 2013
Load bearing of stacked containers shown is at the 40 ft coupling. The two 20‑foot containers at the bottom are rigidly joined with four twistlocks between them, so that they could also be placed higher in the stack. Note: 48-foot and 53-foot units can only be stacked in a 40-foot compliant stack if they are just 8 feet wide, or have special structural provisions to handle their usual 6 inch (15.2 cm) extra width. This is usually not the case. Not shown is the rare, but also possible combination of a 30-foot container coupled to a 10-foot box, in a 40(+) foot long stack.