GMC 2006 Envoy Owner's Manual page 45

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 Should I Use a Child Restraint?
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. To help reduce
injuries, an add-on child restraint must be secured
in the vehicle. With built-in or add-on child
restraints, the child has to be secured within the
child restraint.
When choosing an add-on child restraint, be sure
the child restraint is designed to be used in a
vehicle. If it is, it will have a label saying that it
meets federal motor vehicle safety standards. Then
follow the instructions for the restraint. You may
find these instructions on the restraint itself or in a
booklet, or both.
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