Chevrolet 2001 Monte Carlo Owner's Manual page 68

D
If your vehicle doesn't have the child restraint
locking feature on the shoulder belt retractor,
tighten the belt by pulling up on the shoulder belt
while you push down on the child restraint. You
may find it helpful to use your knee to push down
on the child restraint as you tighten the belt.
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6. Push and pull the child restraint in different
directions to be sure it is secure.
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.