Buick 2005 LaCrosse Owner's Manual page 320

The adjustment screw can be turned with a 6 mm
male hex.
To adjust the vertical aim on the headlamps, do the
following:
1. Find the aim dot on the lens of the low-beam lamp.
5-44
2. Measure the distance from the ground to the aim
dot on the lamp. Record the distance.
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.