You want to couple up a trailer with ball coupling. What is correct?

When coupling a trailer with a ball coupling in Germany, it is essential for safety and legal reasons that the claw of the coupling fits securely around the ball, and the locking device is properly engaged. This ensures the trailer is firmly attached and won't detach while driving. Additionally, the trailer's electrical connection must be established so that brake lights, indicators, and other signals function correctly. The jack wheel, however, should be raised and secured before driving, not set to run, to avoid damage and unsafe conditions. Therefore, the correct procedure includes secure mechanical coupling and electrical connection, but not leaving the jack wheel in a position that allows it to run on the road.