Chevrolet 2003 Astro Owner's Manual page 27

Shoulder Belt Height Adjuster
To move it down, push it in at the top of the arrows
and move the height adjuster to the desired position.
Before you begin to drive, move the shoulder belt
You can move the adjuster up just by pushing up on the
adjuster to the height that is right for you.
shoulder belt guide. After you move the adjuster to
your shoulder
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