A weigh bridge is used to weigh a loaded wagon so as to get an idea of the weight of its contents. It is basically a small length of track on a platform that is supported on beams. The beams are located in a pit under the track and rest on knife edges attached to levers. When a wagon is placed on the weigh bridge, its weight is indicated by a pointer on a graduated disc located in an adjoining structure. A weigh bridge is normally provided on a siding and not on a through track.