GMC 2007 Yukon XL Owner's Manual page 45

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 is not long enough,
see Safety Belt Extender on page 60.
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.
5. Move the shoulder belt height adjuster to the
height that is right for you. Improper shoulder
belt height adjustment could reduce the
effectiveness of the safety belt in a crash. See
Shoulder Belt Height Adjustment on page 51.
6. To make the lap part tight, pull up on the
shoulder belt.
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