Chevrolet Corvette 2003 Owner's Manual page 20

The lap part of the belt should be worn low and snug on
the hips, just touching the thighs. In a crash, this
applies force to the strong pelvic bones. And you'd be
less likely to slide under the lap belt. If you slid under it,
the belt would apply force at your abdomen. This
could cause serious or even fatal injuries. The shoulder
belt should go over the shoulder and across the
chest. These parts of the body are best able to take belt
restraining forces.
The safety belt locks if there's a sudden stop or crash,
or if you pull the belt very quickly out of the retractor.
Lap Belt Cinch Feature
If you do not want the lap belt to move freely, pull the
lap belt out all the way to set the lock. To permit the lap
belt to move freely again, unbuckle the belt, let it
retract all the way, and buckle up again.
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