Buick 2002 Rendezvous Owner's Manual page 59

To make the lap belt longer, tilt the latch plate and pull it
along the belt. To make the belt shorter, pull its free end
as shown until the belt is snug.
-
Buckle, position and release the lap shoulder belt the
-
same way as the other lap shoulder belts. 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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