Cadillac 2004 Seville Owner's Manual page 25

Lap-Shoulder Belt
All rear seating positions have lap-shoulder belts. Here
is how to wear one properly.
1. Pick up the latch plate and pull the belt across you.
Do not let it get twisted.
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.
2. Push the latch plate into the buckle until it clicks.
The latch plates in each rear seating position vary
in size. If the center rear or the left rear latch
plate is inserted into the incorrect buckle, the plate
will not latch properly. Be sure you are using
the correct buckle and that the latch plate clicks
when inserted into the buckle.
If the belt stops before it reaches the buckle, tilt the
latch plate and keep pulling until you can buckle it.
Pull up on the latch plate to make sure it is secure.
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