Pontiac 2004 Montana Owner's Manual page 55

To make the belt shorter, pull its free end as shown
until the belt is snug.
Buckle, position and release it the same way as the lap
part of a lap-shoulder belt. If the belt isn't long
enough, see Safety Belt Extender on page 1-56.
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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