Opel 2015 Astra Owner's Manual page 44

42 Seats, restraints
9 Warning
Never store any objects under the
seats.
Drive only with engaged seats and
backrests.
Seat positioning
Pull handle, slide seat, release
handle. Try to move the seat back and
forth to ensure that the seat is locked
in place.
Seat backrests
Pull lever, adjust inclination and
release lever. Allow the backrest to
engage audibly.
Seat height
Lever pumping motion
up = seat higher
down = seat lower