Oldsmobile INTRIGUE 2001 Owner's Manual page 41

On some vehicles, when the shoulder belt is pulled
out all the way, it will lock. If it does, let it go back
all the way and start again. If the belt is not long
enough, see "Safety Belt Extender" at the end of this
section. Make sure the release button on the buckle is
positioned so you would be able to unbuckle the
safety belt quickly if you ever had to.
3. To make the lap part tight, pull down on the buckle
end of the belt as you pull up on the shoulder part.
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 a crash,
or if you pull the belt very quickly out of the retractor.
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