GMC 2010 Yukon XL Denali Owner's Manual page 74

4. If equipped with a shoulder belt height adjuster,
move it to the height that is right for you. See
Shoulder Belt Height Adjustment later in this
section for instructions on use and important
safety information.
5. To make the lap part tight, pull up on the
shoulder belt.
It may be necessary to pull stitching on the safety
belt through the latch plate to fully tighten the lap
belt on smaller occupants.
2-42
To unlatch the belt, push the button on the buckle. The
belt should return to its stowed position.
Before a door is closed, be sure the safety belt is out of
the way. If a door is slammed against a safety belt,
damage can occur to both the belt and the vehicle.