It is used to reduce the weight of the structure. The sandwich structure of high-strength steel plate and aluminum plate can ensure the rigidity and safety of the car body, but the more materials, the greater the weight, which is not conducive to improving the handling and fuel efficiency of the vehicle. The process of setting some holes and thinning in the sandwich structure is to reduce the weight. In the design of the rear fender of Golf 8, the holes in the sandwich structure can not only reduce the weight of the car body, but also improve the overall stability and reduce the wind resistance, thus better improving the driving performance and driving experience of the vehicle.