A cage under hook is a work platform designed to be lifted directly by the main crane hook rather than by a container spreader. It provides a secure environment for carrying out inspections, maintenance, lashing and general tasks at height in ports, shipyards and industrial facilities. Because it does not depend on a spreader interface, a hook-suspended cage is compatible with a broader range of cranes, including mobile harbour cranes and shipyard cranes. These cages usually incorporate automatic locking mechanisms, redundant safety systems, anti-tilt designs and certified anchor points for personal protective equipment. They are commonly used when container spreaders are unavailable or when the task requires manoeuvrability beyond the reach of standard container-handling equipment.