Cadillac 2007 CTS Owner's Manual page 27

The shoulder belt may lock if you pull the belt
across you very quickly. If this happens, let
the belt go back slightly to unlock it. Then pull
the belt across you more slowly.
4. Push the latch plate into the buckle until it
clicks.
Pull up on the latch plate to make sure it is
secure. If the belt is not long enough,
see Safety Belt Extender on page 41.
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.
5. To make the lap part tight, pull up on the
shoulder belt.
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