Opel Astra 2013 Owner's Manual page 224

222 Driving and operating
Disengage and fold down the socket.
Remove the sealing plug from the
opening for the coupling ball bar and
stow it.
Checking the tensioning of the
coupling ball bar
■ Red marking on rotary knob must
point towards green marking on
coupling ball bar.
■ The gap between the rotary knob
and the coupling ball bar must be
approx. 6 mm.
■ The key must be in position c.
Otherwise, the coupling ball bar must
be tensioned before being inserted:
■ Unlock coupling ball bar by turning
key to position c.
■ Pull out rotary knob and turn
clockwise as far as it will go.
Inserting the coupling ball bar
Insert the tensioned coupling ball bar
in the opening and push firmly
upwards until it audibly engages.
The rotary handle snaps back into its
original position resting against the
coupling ball bar without a gap.
9 Warning
Do not touch rotary handle during
insertion.
Lock the coupling ball bar by turning
the key to position e. Remove the key
and close the protective flap.