This is a trolley for floating of a jammed axle/wheel.If the axle/wheel of a locomotive is jammed on the line then this trolley is sent.The wheels of the loco are lifted with jacks and then this trolley is inserted beneath them.When the wheel is lowered again,it rests on the small rollers.This way the loco can be towed to the loco shed for repairs. (Khalid Kagzi)