Mercedes-Benz 300 SL Operator's Manual page 36

Backrest
Folding forward:
Lift lever and fold forwards.
Folding back:
Fold backrest back until it audibly
locks in place.
Warning!
The seat belts provide protection
only with the backrest locked in
place and, therefore, must be locked
in place with the vehicle in motion.
Do not drive the car when the seat-
back is not locked in place.
Note:
If the backrest and seat belt warning
lamp does not go out, but is instead lit
continuously, then a backrest is not
engaged in its lock.
Always provide sufficient room behind
the backrest and fold the backrest all
the way back until it can be heard
locking in place.
The warning lamp goes out as soon as
both backrests are locked in place.
If both backrests are locked in place
and the warning lamp does not go out,
have the system checked at your
authorized Mercedes-Benz dealer
immediately.
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