Rear Safety Belt Comfort Guides - GMC 2007 Yukon XL Owner's Manual

The safety belt locks if there is a sudden stop or a
crash, or if you pull the belt very quickly out of
the retractor.
CAUTION:
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You can be seriously hurt if your shoulder
belt is too loose. In a crash, you would
move forward too much, which could
increase injury. The shoulder belt should
fit against your body.
56
To unlatch the belt, push the button on the buckle.

Rear Safety Belt Comfort Guides

Rear shoulder belt comfort guides may provide
added safety belt comfort for older children
who have outgrown booster seats and for some
adults. When installed on a shoulder belt, the
comfort guide positions the belt away from
the neck and head.