What must you do after coupling up a single-axle trailer with overrun brakes?

Your answer is fully correct. When coupling a single-axle trailer with overrun brakes, you must always check that the brakes are working to ensure safety during driving. Raising the jack wheel to the highest position is necessary to prevent it from touching the ground while driving. Attaching the breakaway cable to the towing vehicle’s coupling is crucial because it engages the trailer’s brakes if the trailer accidentally disconnects, helping to prevent accidents. These steps are required by law to ensure the safe and secure attachment of the trailer. Always remember to perform all these actions before setting off with a trailer.