What is the primary purpose of filler in collision repair?

The primary purpose of filler in collision repair is indeed to repair dents and imperfections in the vehicle's body before painting. In the context of auto body repair, fillers are materials such as body filler or putty that are applied to surfaces to create a smooth, even finish. They effectively fill in areas where material has been lost or where there are surface irregularities caused by dents, scratches, or other damages.

Using filler is an important step in the collision repair process, as it ensures that the surface of the vehicle is uniformly smooth, allowing for better adhesion of paint and a more aesthetically pleasing final appearance. After the filler is applied, it is typically sanded down to match the surrounding area seamlessly, further enhancing the overall quality of the repair.

The other options do not accurately describe the function of filler. Enhancing vehicle speed, cleaning surfaces, or strengthening the frame are not related to the primary role of filler in the repair process. Instead, they pertain to different aspects of vehicle performance and maintenance.