FORD 2011 F-550 v.2 - Manual (Page 171)

WARNING: Do not use extensions to change the fit of the
shoulder belt across the torso.
Front safety belt height adjustment
Your vehicle has safety belt height
adjustments at the front outboard
seating positions. Adjust the height
of the shoulder belt so the belt rests
across the middle of your shoulder.
To adjust the shoulder belt height,
pull on the center button and slide
the height adjuster down. Release
the button and pull down on the
height adjuster to make sure it is
locked in place. To adjust the belt
upward, slide the adjuster up and then pull down on the height adjuster
to make sure it is locked in place
WARNING: 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 safety
belt and increase the risk of injury in a collision.
Safety belt warning light and indicator chime
The safety belt warning light illuminates in the instrument cluster and a
chime sounds to remind the occupants to fasten their safety belts.
Seating and Safety Restraints
171
2011 F-250/350/450/550 (f23)
Owners Guide, 2nd Printing
USA (fus)