The goods were moved by rail to their destination, were the process was repeated to unload the boxcars. This loading and unloading took a lot of time. Nowadays, the goods are packed into a container, which is a big box shape, the size of a truck trailer. The container is moved from truck or boats to railroad cars by picking the whole container up with a big crane or special, big, forklift. This save time, manpower and money.
Rotary dumpers can turn a car upside down and put it back without uncoupling.
This means the train car couplers had to be re-designed to rotate.