Buick 1993 Century Owner's Manual page 23

4. Push the seatback all the way up until it locks in the
upright position. Push back and forth on the seatback
to be sure it is locked in place.
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. .
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I .
To Lower the Rear-Facing Third Seatback:
1. Open the liftgate and lift the seat release lever located
at the lower corner of the storage compartment on the
passenger side.
2 1