Buick 2006 LaCrosse Owner's Manual page 344

3. At the wall or other flat surface, measure from the
ground upward the recorded distance from Step 2
and draw or tape a horizontal line the width of
the vehicle.
4. Turn on the low-beam headlamps and place a
piece of cardboard or equivalent in front of the
headlamp not being aimed. This should allow
only the beam of light from the headlamp being
aimed to be seen on the flat surface.
5-50
Notice: Do not cover a headlamp to improve beam
cut-off when aiming. Covering a headlamp may
cause excessive heat build-up which may cause
damage to the headlamp.
5. Turn the vertical aiming screw until the headlamp
beam is aimed to the horizontal tape line. The
top edge of the cut-off should be positioned at the
bottom edge of the horizontal tape line.
6. Repeat Steps 4 and 5 for the opposite headlamp.