Pontiac Aztek 2003 Owner's Manual page 34

The lap part of the belt should be worn low and
snug on the hips, just touching the thighs.
1-28
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 a
crash, or if you pull the belt very quickly out of
the retractor.
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CAUTION:
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.