GMC 2010 T-Series Owner's Manual page 39

4. Push the latch plate into the buckle until it clicks.
Make sure the release button is positioned so you
would be able to unbuckle the safety belt quickly if
necessary.
5. Tighten the belt by pulling its free end while you
push down on the child restraint. 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.
6. Push and pull the child restraint in different
directions to be sure it is secure.
To remove the child restraint, unbuckle the vehicle's
safety belt.
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