GMC 2009 Sierra 1500 Crew Cab Owner's Manual page 37

3. 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 1-37.
If the latch plate will not go fully into the buckle,
check if the correct buckle is being used.
Position the release button on the buckle so that
the safety belt could be quickly unbuckled if
necessary.
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.
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.
1-31