The container ship is a specialized cargo vessel that carry all its cargo in either 20-foot or 40-foot intermodal containers. The capacity of a container ship is usually expressed in 20-foot equivalent units (TEU), i.e., the number of containers of that size it can carry. Container ships vary greatly in size, depending on the service they provide: major port calls, short sea shipping and feeders. They are also differentiated by the presence or absence of cranes.
Different types of container ship are designed for varying needs. There are specialized container ships for refrigerated containers, geared feeder container vessels able to operate in ports without port cranes and large container ships without cranes.
Container ships have one or more cargo holds provided with rails in order to guide containers into well-defined rows during the loading process. These holds are topped by hatch covers, onto which more containers can be loaded and secured. Containers stowed on deck must be secured with lashing systems, locking systems, and buttress systems.
Container capacity is the main consideration. Route, navigational zone and scope, the need of deck cranes and many other factors also must be taken into account.
