FORD 2001 F-150 v.1 - Manual (Page 83)

The safety belt pretensioner is a device which removes excess webbing
from the safety belt system. The safety belt pretensioner uses the same
crash sensor system as the front air bag supplemental restraint system
(SRS). When the safety belt pretensioner deploys, webbing from the lap
and shoulder belt is tightened. The driver and front passenger seat belt
system (including retractors, buckles and height adjusters) must be
replaced if the vehicle is involved in a collision that results in
deployment of front air bags and safety belt pretensioners.
Safety belt height adjustment
Your vehicle has safety belt height
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.
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 shoulder 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
83