Ford Mercury Villager 1997 Owner's Manual page 171

If the shoulder belt portion of one of the lap/shoulder
belts can be positioned so that it does not cross or rest in
front of the child's face or neck, the child should wear
the lap/shoulder belt. Moving the child closer to the center
of the vehicle may help provide a good shoulder belt
fit.
To improve the fit of lap and shoulder belts on children who
have outgrown child safety seats, Ford recommends use of a
belt-positioning booster seat that is labelled as conforming to all
Federal motor vehicle safety standards. Belt-positioning
booster seats raise the child and provide a shorter, firmer seating
cushion that encourages safer seating posture and better fit of
lap and shoulder belts on the child. A belt-positioning booster
should be used if the shoulder belt rests in front of the
child's face or neck, or if the lap belt does not fit snugly on both
thighs, or if the thighs are too short to let the child sit all the
way back on the seat cushion when the lower legs hang over the
edge of the seat cushion. You may wish to discuss the specific
needs of your child with your pediatrician.
Do not use a belt-positioning booster with a lap-only belt.
The lap belt portion of combination lap/shoulder belts
should always be worn snugly and below the hips, touching
the child's thighs.
Seating and Safety Restraints
WARNING
WARNING
WARNING
167