Formed by a combination of fixed mounted-type with the mono-rail element and is operated on the bottom of the single girder and the wheel is made of mono-block medium carbon steel with the surface being processed with hardness treatment; installed with anti-drop steel plate and buffer rubber pad which is safe and reliable; two drive wheels makes the move more stable and smooth can be applied to machines with a beam bending radius of 1.5 ~ 3.0 meters and is appropriate for workstation crane.