Cadillac 1999 DeVille Owner's Manual page 55

5. Pull the rest of the lap belt all the way out of the
retractor to set the lock.
6. To tighten the belt, feed the lap belt back into the
retractor 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.
7. 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.
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