GMC Sierra Denali 2009 Owner's Manual page 57

If the child restraint manufacturer recommends using a
top tether, attach and tighten the top tether to the top
tether anchor. Refer to the instructions that came with the
child restraint and see Lower Anchors and Tethers for
Children (LATCH) on page 1-43.
1. Put the child restraint on the seat.
2. Pick up the latch plate, and run the lap and shoulder
portions of the vehicle's safety belt through or around
the restraint. The child restraint instructions will show
you how.
3. Push the latch plate into the buckle until it clicks.
Position the release button on the buckle so that
the safety belt could be quickly unbuckled if
necessary.
4. Pull the rest of the shoulder belt all the way out of
the retractor to set the lock.
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