Oldsmobile 2001 Silhouette - Manual (Page 65)

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Center Passenger Position (Bench Seat) Lap Belt
If your vehicle has a third row rear bench seat, someone
can sit in the center position.
When you sit in the center position of the bench seat,
you have a lap safety belt, which has no retractor.
To make the belt longer, tilt the latch plate and pull it
along the belt.