Buick 2004 Rendezvous Owner's Manual page 77

5. To tighten the belt, pull 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.
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.
1-71