Chevrolet 2005 Tahoe Owner's Manual page 66

The center seat position in the third row has a lap belt.
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.
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3. Run the vehicle's safety belt through or around the
restraint. The child restraint instructions will show
you how.
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.