Specially designed devices that hold trucks or trolleys (with castors fitted) in a fixed position during loading or unloading. They are designed to enable a quick and easy change between the locked and free movement modes. All Coldene truck locks are top plate mounted and bolted to the underside of the trolley. The principle on which they work requires a constant gap between the unit and the floor, so it is best to mount the truck lock close to a castor, ensuring that it does not interfere with the free movement and operation of the castor. A step down foot-operated pedal moves a skid-resistant rubber pad into friction contact with the floor surface. This is done with a spring-loaded over-cam mechanism that does not lift the load and keeps the operating force low. It also means the load rating of the trolley is not relevant to the truck lock. A second step down pedal raises the footpad. The limited number of parts means there is less to maintain or go wrong. Where a trolley has four swivel castors, two truck locks are required - one to be fitted at each end, either on the same side or diagonally opposite. Only one truck lock is required at the swivel end of a trolley that has two swivel and two fixed castors.