Container port. Cranes and freight at a container port. Containers are made to a standard size, and allow the shipping of mixed cargoes. Their uniform size makes them easy to handle and load. Each container has a lockable door which may be sealed by customs officials after inspection. At their destination, the containers may be easily sorted for loading onto lorries or train carriages for distribution. Photographed at Bilbao docks. Bilbao is an important sea port with 17km of docks and a registered flow of traffic of 32. 7 million tonnes in 1991.