Pontiac 2002 Aztek Owner's Manual page 26

Shoulder Belt Height Adjuster
Before you begin to drive, move the shoulder belt
adjuster to the height that is right for you.
To move it down, push down on the button and move
the height adjuster to the desired position.
1-20
You can move the adjuster up just by pushing up on the
shoulder belt guide. After you move the adjuster to
where you want it, try to move it down without pushing
the button down to make sure it has locked into position.
Adjust the height so that the shoulder portion of the
belt is centered on your shoulder. The belt should be
away from your face and neck, but not falling off
your shoulder.