Buick 2010 Lucerne Owner's Manual page 419

To reinstall the rear seat cushion, do the following:
WARNING:
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A safety belt that is not properly routed through
the seat cushion or is twisted will not provide the
protection needed in a crash. If the safety belt has
not been routed through the seat cushion at all, it
will not 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. Do not 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.
3. With the seat cushion lowered, push rearward and
then press down on the seat cushion until the
spring locks on both ends engage.
4. Check to make sure the safety belts are properly
routed and that no portion of any safety belt is
trapped under the seat. Also make sure the seat
cushion is secured.
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