FORD 2011 F-550 v.4 - Manual (Page 209)

Child booster seats
The belt-positioning booster (booster seat) is used to improve the fit of
the vehicle safety belt. Children outgrow a typical child seat (e.g.,
convertible or toddler seat) when they weigh about 40 lb (18 kg) and are
around four (4) years of age. Consult your child safety seat owner guide
for the weight, height, and age limits specific to your child safety seat.
Keep your child in the child safety seat if it properly fits the child,
remains appropriate for their weight, height and age AND if properly
secured to the vehicle.
Although the lap/shoulder belt will provide some protection, children
who have outgrown a typical child seat are still too small for lap/shoulder
belts to fit properly, and wearing an improperly fitted vehicle safety belt
could increase the risk of serious injury in a crash. To improve the fit of
both the lap and shoulder belt on children who have outgrown child
safety seats, Ford Motor Company recommends use of a belt-positioning
booster.
Booster seats position a child so that vehicle lap/shoulder safety belts fit
better. They lift the child up so that the lap belt rests low across the hips
and the knees bend comfortably at the edge of the cushion, while
minimizing slouching. Booster seats may also make the shoulder belt fit
better and more comfortably. Try to keep the belt near the middle of the
shoulder and across the center of the chest. Moving the child closer (a
few centimeters or inches) to the center of the vehicle, but remaining in
the same seating position, may help provide a good shoulder belt fit.
When children should use booster seats
Children need to use booster seats from the time they outgrow the
toddler seat until they are big enough for the vehicle seat and
lap/shoulder belt to fit properly. Generally this is when they reach a
height of at least 4 feet 9 inches (1.45 meters) tall (around age eight to
age twelve and between 40 lb (18 kg) and 80 lb (36 kg) or upward to
100 lb (45 kg) if recommended by your child restraint manufacturer).
Many state and provincial laws require that children use approved
booster seats until they reach age eight, a height of 4 feet 9 inches
(1.45 meters) tall, or 80 lb (36 kg).
Seating and Safety Restraints
209
2011 F-250/350/450/550 (f23)
Owners Guide, 4th Printing
USA (fus)