The sled is chained and electronically attached to the tractor. At the start, additional loads are placed on the sled. As it moves forward, the sled moves is moving the weight box from axle at the rear to pan at the front. This builds resistance, making it increasingly challenging. After each round, the track is completely cleared so that all competitors have a level playing field.
European tractor pulling usually comprises two rounds: a qualifier and the final. To qualify, tractors must arrive within 100 metres to advance to the final. This is known as the Full Pull and is the goal of every competitor.