A loader crane (also called a knuckle-boom crane or articulating crane) is an electrically or PTO powered articulated arm fitted to a truck or trailer, and is used for loading/unloading the vehicle. Unlike most cranes, the operator must move around the vehicle to be able to view his load; hence modern cranes may be fitted with a portable cabled or radio-linked control system to supplement the crane-mounted hydraulic control levers. In the UK this type of crane is often known colloquially as a "Hiab", partly because this manufacturer invented the loader crane and was first into the UK market. walls.