Off-track operation on the main beam, similar to L-type gantry crane. The advantage is that the car runs smoothly, and the same elevation of the big car runs the track surface, and the lifting height can be increased by 1.5 to 1.8 meters. The shortage is that the production is more complicated than the hanging process, and the production cost is higher. It is widely used in mechanical manufacturing, assembly, production workshops and warehouses, and its fetching device is usually a hook.