Buick 1999 Riviera Owner's Manual page 41

4. Buckle, position and release the safety belt as
described in "Rear Seat Outside Passenger Positions"
earlier in this section. Make sure that the shoulder
belt crosses the shoulder.
To remove and store the comfort guides, squeeze
the belt edges together so that you can take them out
from the guides. Pull the guide upward to expose its
storage clip, and then slide the guide onto the clip.
Rotate the guide and clip inward and in between the
seatback and the interior body, leaving only the loop of
elastic cord exposed.
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