Buick 2000 Regal Owner's Manual page 26

Adjust the height so that the shoulder portion of the belt is
centered on your shoulder. The belt should be away from
your face and neck, but not falling off your shoulder.
Q:
What's wrong with this?
A:
The shoulder belt is too loose. It won't give nearly
as much protection this way.
1-14
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.