GMC 2004 Sierra 1500 Pickup Owner's Manual page 66

5. To tighten the belt, pull its free end while you push
down on the child restraint. If you're using a
forward-facing child restraint, you may find it helpful
to use your knee to push 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. It will be ready to work for an adult or
larger child passenger.
1-60
Securing a Child Restraint in the
Center Front Seat Position
Don't use child restraints in this position. The restraints
won't work properly.