Pontiac 2006 Montana SV6 Owner's Manual page 42

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
would 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.
1-36
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:
{
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.
To unlatch the belt, push the button on the buckle.