GMC 2007 Sierra - Manual (Page 82)

3. Pick up the latch plate, and run the lap and
shoulder portions of the vehicle’s safety belt
through or around the restraint. The child
restraint instructions will show you how.
4. Buckle the belt. Make sure the release button
is positioned so you would be able to unbuckle
the safety belt quickly if you ever had to.
5. Pull the rest of the shoulder belt all the way
out of the retractor to set the lock.
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