GMC 2005 Safari Owner's Manual page 49

A booster seat (F-G) is a child restraint designed to
improve the fit of the vehicle's safety belt system.
Some booster seats have a shoulder belt positioner,
and some high-back booster seats have a five-point
harness. A booster seat can also help a child to see
out the window.
Q:
How do child restraints work?
A:
A child restraint system is any device designed for
use in a motor vehicle to restrain, seat, or position
children. A built-in child restraint system is a
permanent part of the motor vehicle. An add-on
child restraint system is a portable one, which
is purchased by the vehicle's owner.
For many years, add-on child restraints have
used the adult belt system in the vehicle. To help
reduce the chance of injury, the child also has to
be secured within the restraint. The vehicle's
belt system secures the add-on child restraint in
the vehicle, and the add-on child restraint's harness
system holds the child in place within the restraint.
One system, the three-point harness, has straps
that come down over each of the infant's shoulders
and buckle together at the crotch. The five-point
harness system has two shoulder straps, two hip
straps and a crotch strap. A shield may take
the place of hip straps. A T-shaped shield has
shoulder straps that are attached to a flat pad which
rests low against the child's body. A shelf- or
armrest-type shield has straps that are attached
to a wide, shelf-like shield that swings up or to
the side.
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