twistlock and corner casting

thumb|left|Close-up of twistlock on a rear corner of a German Container chassis|semi-trailer thumb|Close up of top corner casting on an ISO shipping container. The twistlock proper is inserted through the large oval hole in the top of upper, and the bottom of the lower corner castings.

A twistlock or twist lock, together with matching corner castings, as defined in norms including ISO 1161:1984, form a standardized (rotating) connector system, for connecting and securing intermodal, and predominantly ISO-standard international shipping containers. The primary uses are to securely stack containers, for locking them into place on a container ship, semi-trailer or rail carriage, and for lifting and handling by specific container-handling equipment, like straddle carriers, reach stackers, container-handling forklifts, sidelifters, and various types of container cranes.