The adjustment procedure for headlights on Cobalt/GS and ION models involves locating the vertical adjustment screws behind each headlight housing, while on HHR models, the vertical adjustment screw is found under the inner fender flange. There are no horizontal adjustment screws. To adjust the headlights, one method involves using masking tape, a blank wall, and a level floor. The tape is positioned vertically on the wall in reference to the vehicle centerline and the centerlines of both headlights, and a horizontal tape line is positioned in reference to the centerline of all the headlights. The vehicle should be parked 25 feet from the wall, sitting level, with the gas tank half-full and no heavy load in the vehicle. Starting with the low beam adjustment, the high intensity zone should be positioned two inches below the horizontal line, and adjustment is made by turning the adjusting screw. With the high beams on, the high intensity zone should be vertically centered with the exact center just below the horizontal line. It is important to note that it may not be possible to position the headlight aim exactly for both high and low beams, and if a compromise must be made, prioritizing the proper aim of the low beams is recommended for safety. It is advised to have the headlights adjusted by a dealer service department or service station as soon as possible.