GMC 2007 Sierra - Manual (Page 83)

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.
7. If your child restraint manufacturer
recommends using a top tether, and the
position you are using has a top tether anchor,
attach and tighten the top tether to the top
tether anchor. Refer to the instructions
that came with the child restraint and to Lower
Anchors and Tethers for Children (LATCH)
on page 58.
8. Push and pull the child restraint in different
directions to be sure it is secure.
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