GMC Yukon XL 2013 Owner's Manual page 121

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. For passenger seating positions
with a lap-shoulder belt and a
free-falling latch plate, pull the
rest of the shoulder belt all the
way out of the retractor to set
the lock. When installing a child
restraint using a lap-shoulder
belt and a cinching latch plate,
skip Step 4 and proceed to
Step 5.
Seats and Restraints
5. To tighten the belt, push down
on the child restraint, pull the
shoulder portion of the belt to
tighten the lap portion of the belt
and feed the shoulder belt back
into the retractor. When installing
a forward-facing child restraint, it
may be helpful to use your knee
to push down on the child
restraint as you tighten the belt.
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