Opel Vivaro Owner's Manual page 51

Longitudinal adjustment
Pull the handle, slide the seat, then
release the handle. Try to move the
seat back and forth to ensure that the
seat is locked in place.
Backrest inclination
Turn handwheel to adjust inclination.
Do not lean on the backrest while
adjusting.
Seats, restraints
Seat height
Lever pumping motion
up : seat higher
down : seat lower
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