Pontiac 2001 Aztek Owner's Manual page 56

The lap part of the belt should be worn low and snug on
3. To make the lap part tight, pull down on the buckle
the hips, just touching the thighs. In a crash, this applies
end of the belt as you pull up on the shoulder part.
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.
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