Cadillac CTS Owner's Manual page 36

3. To make the lap part tight, pull down on the
buckle end of the belt as you pull up on the
shoulder part.
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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.