A freight-carrying unit optimised to road vehicle dimensions and fitted with handling devices for transfer between modes, usually road/rail. Such units were not originally designed to be stacked when full or top-lift ed. Many units now can be, although not to the same extent as containers. The main feature distinguishing them from containers is that they are optimised to road vehicle dimensions. Such unit would need UIC approval to be used on rail. Some swap bodies are equipped with folding legs on which the unit stands when not on the vehicle.