Chevrolet 2005 Tahoe Owner's Manual page 34

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 will
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 is a sudden stop or
a crash.
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