GMC Sierra 2014 Owner's Manual page 75

For the lap-shoulder belt in the
rear center seating position of a
crew cab, if the webbing locks in
the latch plate before it reaches
the buckle, tilt the latch plate flat
to unlock.
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 3-20.
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.
Seats and Restraints
4. If equipped with a shoulder belt
height adjuster, move it to the
height that is right for you. See
Shoulder Belt Height Adjuster
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.
3-15