FORD 2011 F-550 v.4 - Manual (Page 169)

3. Insert the belt tongue into the proper buckle for your seating position
until you hear a snap and feel it latch.
4. Make sure the tongue is securely fastened to the buckle by pulling on
the tongue.
WARNING: The lap belt should fit snugly and as low as possible
around the hips, not across the waist.
WARNING: Front and rear seat occupants, including pregnant
women, should wear safety belts for optimum protection in an
accident.
WARNING: Each seating position in your vehicle has a specific
safety belt assembly which is made up of one buckle and one
tongue that are designed to be used as a pair. 1) Use the shoulder belt
on the outside shoulder only. Never wear the shoulder belt under the
arm. 2) Never swing the safety belt around your neck over the inside
shoulder. 3) Never use a single belt for more than one person.
While you are fastened in the safety belt, the combination lap/shoulder
belt with a cinch tongue adjusts to your movement. However, if you
brake hard, turn hard, or if your vehicle receives an impact of 5 mph
(8 km/h) or more, the safety belt will become locked and help reduce
your forward movement.
Restraint of pregnant women
WARNING: Always ride and drive with your seatback upright
and the safety belt properly fastened. The lap portion of the
safety belt should fit snug and be positioned low across the hips. The
shoulder portion of the safety belt should be positioned across the
chest. Pregnant women should also follow this practice. See figure
below.
Seating and Safety Restraints
169
2011 F-250/350/450/550 (f23)
Owners Guide, 4th Printing
USA (fus)