FORD 2003 F-150 v.1 - Manual (Page 104)

Front safety belt height adjustment (if equipped)
If your shoulder belts come out of the front seat back, you will not have
a safety belt height adjuster.
Regular Cab and SuperCab vehicles have safety belt height adjustments
for the driver and front passenger. SuperCrew vehicles have these
adjustments for the driver, front passenger and rear outboard
passengers. Adjust the height of the shoulder belt so the belt rests
across the middle of your shoulder.
• Regular Cab/4–door SuperCrew
• 4–door SuperCab (Bench seats
only)
To lower the shoulder belt height, push the button and slide the height
adjuster down. To raise the height of the shoulder belt, slide the height
adjuster up. Pull down on the height adjuster to make sure it is locked in
place.
Position the safety belt height adjusters so that the belt rests
across the middle of your shoulder. Failure to adjust the safety
belt properly could reduce the effectiveness of the seat belt and
increase the risk of injury in a collision.
Seating and Safety Restraints
104