Mercedes-Benz GL Operator's Manual page 166

Setting the air vents
164
To open/close: turn thumbwheel ; to the
X
left or right.
B-pillar air vent in the headliner
Rear air vent
:
Thumbwheel for rear air vent
;
To open/close: turn thumbwheel ; up or
X
down.
Third row of seats
B-pillar air vent in the headliner
Rear air vent
:
Thumbwheel for rear air vent
;
To open/close: turn thumbwheel ; up or
X
down.