2001 Cadillac DeVille Owner's Manual - Page 350

3. At the wall or other flat surface, measure from the floor to the recorded distance and draw a horizontal line the width of the vehicle. NOTICE: Do not cover a headlamp to improve beam cut-off when diming. Covering a headlamp may cause excessive heat build-up which may cause damage to the headlamp. 4. Turn on the low beam headlamps and place a piece of cardboard or equivalent in front of the headlamp not being dimed. This should allow the beam cut-off of the headlamp being aimed to be seen on the flat surface. 6-42