Buick 2002 LeSabre Owner's Manual page 310

Headlamp Vertical Aiming
NOTICE:
Horizontal aiming must be performed before
making any adjustments to the vertical aim.
Adjusting the vertical aim first will result in
an incorrect headlamp aim.
1. Find the aim dot on the lens of the low beam lamps.
2. Measure the distance from the ground to the aim dot
on each lamp; if left low beam, subtract two inches.
Record this distance.
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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.
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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.