Pontiac 2002 Bonneville Owner's Manual page 335

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.
6-40
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.