Cadillac GMC Yukon Denali 2005 Owner's Manual page 72

If your child restraint does not have the LATCH system,
you will be using a lap belt to secure the child restraint
in the center seat position in the third row. Be sure
to follow the instructions that came with the child
restraint. Secure the child in the child restraint when
and as the instructions say.
1. Make the belt as long as possible by tilting the latch
plate and pulling it along the belt.
2. Put the child restraint on the seat.
3. Run the vehicle's safety belt through or around the
restraint. The child restraint instructions will show
you how.
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4. Buckle the belt. Make sure the release button is
positioned so you would be able to unbuckle the
safety belt quickly if you ever had to.
5. To tighten the belt, pull its free end while you push
down on the child restraint. If you are using a
forward-facing 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. It will be ready to work for an adult or
larger child passenger.