Aim the headlights on a General Motors vehicle using screwdrivers, masking tape, a vertical wall and a level surface. Some GM headlights require a special head screwdriver to turn the adjusting screws. Begin the job by parking the vehicle close to the wall, turning on the headlights and marking the center of each headlight beam with an "X" formed out of tape.
If the vehicle has single-bulb headlights, make one "X" at each side. For dual-beam headlights, make a mark for both high and low beams. Also mark the center of the vehicle on the wall. Back the vehicle approximately 25 feet straight back so the center remains in the same location and the car is perpendicular to the wall.
Turn on the low-beam headlights, and check them against the tape marks made earlier. If the center of the beam remains in the same location, there is no need for adjustment. If it moves, turn the adjusting screw using the appropriate tool, and aim it to center the beam on the mark. Repeat the process with the other headlight. For dual-beam headlights, turn the lights on bright, and adjust the screws for the high beams so they are centered on the tape marks.