Auto body frame pullers have towers that connect to the frame with chains, and these towers use hydraulic equipment to pull those chains and straighten out the frame. Features and usage vary somewhat depending on the machine.
Auto technicians use auto body frame pullers to straighten car frames that were damaged. An auto body frame puller typically has a platform for the car. Once the technician drives the car onto the platform, he secures it with clamps so the car can't move during the process. With the car secure, he connects chains from one or more of the machine's towers onto the car. If straightening the frame requires pulling at multiple points, the technician connects chains to each point.
Advanced auto body frame pullers use lasers and ultrasound equipment combined with a computer to determine the extent of a car's damage. This information helps the auto technician determine the time and cost for repair. It also helps the technician perform the repair correctly, through a live mapping system that tracks changes to the frame during the pulling process.
The hydraulic equipment in an auto body frame puller increases tension as necessary to straighten the frame. The maximum pulling power varies depending on the machine.