GMC 2004 Yokon Denali Owner's Manual page 38

3. Pick up the latch plate and pull the belt across you.
Don't let it get twisted.
4. Push the latch plate into the buckle until it clicks.
Pull up on the latch plate to make sure it is secure.
If the belt isn't long enough, see Safety Belt
Extender on page 1-49.
Make sure the release button on the buckle is
positioned so you would be able to unbuckle the
safety belt quickly if you ever had to.
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5. To make the lap part tight, pull down on the buckle
end of the belt as you pull up on the shoulder belt.