GMC 2007 Savana - Manual (Page 71)

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 portion of the belt
to tighten the lap portion of the belt, 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 from the retractor
once the lock has been set.
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