Twistlock in the context of ISO container

An intermodal container, often called a shipping container, or a freight container, (or simply "container") is a large metal crate designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport – such as from ships to trains to trucks – without unloading and reloading their cargo. Intermodal containers are primarily used to store and transport materials and products efficiently and securely in the global containerized intermodal freight transport system, but smaller numbers are in regional use as well. It is like a boxcar that does not have wheels. Based on size alone, up to 95% of intermodal containers comply with ISO standards, and can officially be called ISO containers. These containers are known by many names: cargo container, sea container, ocean container, container van or sea van, sea can or C can, or MILVAN, or SEAVAN. The term CONEX (Box) is a technically incorrect carry-over usage of the name of an important predecessor of the ISO containers: the much smaller steel CONEX boxes used by the U.S. Army.

Intermodal containers exist in many types and standardized sizes, but 90 percent of the global container fleet are "dry freight" or "general purpose" containers: durable closed rectangular boxes, made of rust-retardant weathering steel; almost all 8 feet (2.4 m) wide, and of either 20 or 40 feet (6.1 or 12.2 m) standard length, as defined by International Organization for Standardization (ISO) standard 668:2020. The worldwide standard heights are 8 feet 6 inches (2.6 m) and 9 feet 6 inches (2.9 m) – the latter are known as High Cube or Hi-Cube (HC or HQ) containers. Depending on the source, these containers may be termed TEUs (twenty-foot equivalent units), reflecting the 20- or 40-foot dimensions.

A container crane (also container handling gantry crane or ship-to-shore crane) is a type of large dockside gantry crane found at container terminals for loading and unloading intermodal containers from container ships.

Container cranes consist of a supporting framework that can traverse the length of a quay or yard on a rail track. Instead of a hook, they are equipped with a specialized handling tool called a spreader. The spreader can be lowered on top of a container and locks onto the container's four locking points ("corner castings") using a twistlock mechanism. Cranes normally transport a single container at once, but some newer cranes have the capability to pick up two to four 20-foot containers at once.

A container spreader is a tool used for lifting containers and unitized cargo. The spreader is placed between the container and the lifting machine.

The spreader used for containers has a locking mechanism at each corner that attaches to the four corners of the container. A spreader can be used on a container crane, a straddle carrier and with any other machinery to lift containers. Spreader operation can be manual, semiautomatic or fully automatic.