You want to park your single-axle trailer (overrun brakes, 1000 kg permissible total mass) on a slope. What must you do?

When parking a trailer on a slope, it's essential to ensure it remains stationary to prevent rolling. The correct combination of actions involves:

1. **Pulling the parking brake**: This action helps to secure the trailer in place by applying resistance to the wheels.
2. **Placing wheel chocks under the wheels**: This provides additional safety by physically blocking the wheels and preventing any movement.

Both actions are necessary according to German traffic regulations to enhance safety. Engaging the reverse lock, while important in other contexts, is not required for simply parking. Using the brake and chocks together ensures maximum stability and reduces the risk of accidents.