GMC 2007 Savana - Manual (Page 76)

5. 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 belt to tighten the
lap belt portion and feed the shoulder belt
back into the retractor. If you are using
a forward-facing child restraint, you may find
it helpful to use your knee to push down
on the child restraint as you tighten the belt.
You should not be able to pull more of the
belt out of the retractor once the lock has
been set.
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