Hummer 2009 H3 Owner's Manual page 46

1-42 Seats and Restraint System
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. For H3 models, pull the rest of the
shoulder belt all the way out of the
retractor to set the lock.
6. 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.