Buick 2001 Century Owner's Manual page 284

To check the aim, the vehicle should be properly
prepared as follows:
D
The headlamps must be off for one hour prior to
aiming and must remain off during this procedure.
D
The vehicle must have all four tires on a perfectly
level surface.
D
If necessary, pads may be used on an uneven surface.
D
The vehicle should not have any snow, ice or mud
attached to it.
D
The vehicle should be fully assembled and all other
work stopped while headlamp aiming is being done.
D
There should not be any cargo or loading of the
vehicle, except it should have a full tank of fuel and
one person or 160 lbs. (75 kg) on the driver's seat.
D
Close all doors.
D
Tires should be properly inflated.
D
Rock the vehicle to stabilize the suspension.
6-34
Driver's Side Headlamp Shown
A. Vertical Aim Adjustment Screw
B. Horizontal Aim Adjustment Screw
Open the hood and locate the vertical and horizontal
aim indicators. The aiming screw for the vertical aim
indicator (A) is at the center of the headlamp cover
and the aiming screw for the horizontal aim indicator
is on the outboard side of the headlamp cover (B).