GMC Yukon XL Denali Owner's Manual page 116

3-62 Seats and Restraints
You will be using the lap-shoulder
belt to secure the child restraint in
this position. Follow the instructions
that came with the child restraint.
1. Move the seat as far back as it
will go before securing the
forward-facing child restraint.
2. Put the child restraint on
the seat.
3. 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.
4. 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.
5. Pull the shoulder belt all the way
out of the retractor to set the
lock. When the retractor lock is
set, the belt can be tightened but
not pulled out of the retractor.