Pontiac 2002 Montana Owner's Manual page 60

Third Row Outside Passenger Position
3. To make the lap part tight, pull down on the buckle
end of the belt as you pull up on the shoulder part.
Pull up on the latch plate to make sure it is secure.
When the shoulder belt is pulled out all the way, it
will lock. If it does, let it go back all the way and
start again. If the belt is not 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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