GMC C-Series 2001 Owner's Manual page 20

Suspension (B)
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.
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For suspension type seats (B), if the belt stops before
it reaches the buckle, tilt the latch plate and keep
pulling until you can buckle the belt. Pull up on the
latch plate to make sure it is secure. If the belt is
pulled out all the way so that it locks, press down on
the button on the retractor cover to make it retract.
If the belt isn't long enough, see "Safety Belt
Extender" at the end of this section.
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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