Main methods of automobile body maintenance: 1. Use torch flame to heat the drawing center to dark red, but be careful not to melt or burn through the metal plate. The size of the heating range depends on the degree of stretching. The greater the degree of stretching, the larger the heating range, and the diameter is between15 ~ 30 mm. The stretching degree is very small, and the heating range is about10 mm; 2. After heating, quickly tap the periphery of the flushing area and gradually contract to the center of the heating point, forcing the metal structure to contract; 3. When knocking, use a suitable iron pad, knock the back of the part with a wooden stick and cool it, and then gently knock it with a hammer for leveling. The power of knocking should be moderate. Too much knocking will make the contracted part relax again. If only one shrinkage fails to achieve the purpose of setting, the same method can be used for multi-point shrinkage, and flattening correction is carried out every time heating shrinkage is carried out. After heating in mild stretching, cotton yarn can be soaked in cold water or naturally cooled without knocking.