Mercedes-Benz 350 SDL Owner's Manual page 37

Adjust front seat belts so the upper
belt is located as close as possible to
the middle of the shoulder (it should
not touch the neck). For this purpose,
push button (4) and raise or lower belt
outlet (3 positions).
The belt must be pulled snug and
checked for snugness immediately
after engaging it and during driving. If
necessary, tighten the lap portion to a
snug fit by pulling shoulder portion up.
Unfastening
Push in the red button (3) in the belt
buckle (2).
Allow the retractor to completely
rewind the seat belt by guiding the
latch plate (1).
Operation:
The inertia reel stops the belt from
unwinding during sudden vehicle
stops or when quickly pulling on the
belt.
The emergency tensioning retractor
tightens the seat belt upon major
frontal impacts withing the shaded
area as shown on page 38.
The locking function of the reel may
be checked by quickly pulling out the
belt.
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