Pontiac 2004 Bonneville Owner's Manual page 32

To unlatch the belt, just push the button on the buckle.
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Rear Safety Belt Comfort Guides for
Children and Small Adults
Rear shoulder belt comfort guides provide added safety
belt comfort for older children who have outgrown
booster seats and for small adults. When installed on a
shoulder belt, the comfort guide better positions the
belt away from the neck and head.
There is one guide for each outside passenger position
in the rear seat. To provide added safety belt comfort
for children who have outgrown child restraints and
booster seats and for smaller adults, the comfort guides
may be installed on the shoulder belts. Here's how to
install a comfort guide and use the safety belt: