Cadillac 2003 Seville Owner's Manual page 345

To reinstall the rear seat cushion, do the following:
A safety belt that isn't properly routed through
the seat cushion or is twisted won't provide
the protection needed in a crash. If the
safetybelt hasn't been routed through the seat
cushion at all, it won't be there to work for the
next passenger. The person sitting in that
position could be badly injured. After
reinstalling the seat cushion, always check to
be sure that the safety belts are properly
routed and are not twisted.
1. Buckle the center passenger position safety belt,
then route the safety belts through the proper slots in
the seat cushion. Don't let the safety belts get
twisted.
2. Slide the rear of the cushion up and under the
seatback so the rear-locating guides hook into
the wire loops on the back frame.
5-96