The drag (sled) is known as a "weight transfer drag (sled)". This means that, as it is pulled down the track, the weight is transferred (linked with gears to the drag’s (sled) wheels) from over the rear axles and towards the front of the drag (sled). In front of the rear wheels, instead of front wheels, there is a "pan". This is essentially a metal plate, and as the weight moves toward it, the resistance between the pan and the ground builds. The farther the tractor pulls the drag (sled), the more difficult it gets.