2. Fixation of the vehicle. Fixing four tires of the vehicle with a clamp to prevent the vehicle from being dragged during the stretching of the main beam, rotating the straightening and stretching arm to the position of the main beam, and then fixing the next one with a clamp pin to prevent the stretching arm from shaking in the stretching process, so as to fix the straightening and stretching arm with the main beam;
3. Determine the deformation degree of the main girder. For slight, we just need to stretch in the opposite direction of deformation. At the same time, find a measuring point on the car body, measure the diagonal with a box ruler, and stop when the two diagonal lines are stretched to the same length;
4. For the main girder with serious deformation, we need to fix the stretching position with proper fixture, then stretch the deformed main girder straight first, and then stretch it in the opposite direction of the main girder deformation. For the girder with serious deformation, it is necessary to pull it several times, not once, which will do great harm to the whole. Similarly, it is good to draw two diagonal lines to the same length;
5, bar iron length measurement. Measure the length of the screw holes on both sides of the bar iron with a square ruler, and then measure the length of the screw holes on the corresponding two beam heads to see if they are consistent. Error is possible, the error is between 3-5mm, if the length is different, you need to continue stretching until the length is the same;
6. Install the bar iron on the beam heads of two girders, and check whether the beam heads are straight. If the beam head is crooked, the screws of the four screw holes will not be easy to install, so the positions of the two beam heads must be straight. Measure the diagonal again, the bar and iron are suitable, and the rectification of the girder has been basically successful.