Buick 2006 Lucerne Owner's Manual page 365

To reinstall the rear seat cushion, do the following:
CAUTION:
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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.
CAUTION: (Continued)
CAUTION: (Continued)
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 down and under the
seatback.
3. With the seat cushion lowered, push rearward and
then press down on the front of the seat cushion
until the front hooks 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. Pull up on the front of the
seat cushion to make sure it is secured.
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