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.

Plaque marking the building in Prague where the ISO predecessor, the ISA, was founded