GMC 1999 Envoy Owner's Manual page 52

To remove the child restraint, just unbuckle the vehicle's
safety belt and let it go back all the way. The safety belt
will move freely again and be ready to work for an adult
or larger child passenger.
Center Seat Position
Don't use child restraints in this position. The restraints
won't work properly.
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Securing a Child Restraint in the Right
Front Seat Position
Your vehicle has a right front passenger air bag. Never
-
put a rear facing child restraint in this seat. Here's why:
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