GMC 2003 Sierra - Manual (Page 28)

Qi Whal’s wrong with iWs?
You can t>e sarfously fnjurad if you iivear rhe
ahoulder belt under your
^rm. In a crash, your
body would move too far forward, which wou^d
Increase the chance of head and neck Injury,
Also, the bert would appfy loa imuch force to
the ribs, which aren't as strong as shoulder
bones. You could also severely injure Irfternal
organs Ifke your tiver or spleen.
A; The shouJder bell Is worn under the ann. Il should
be Worn over ihe shoulder at all times.