How do you secure a car with a manual gearbox against rolling away on a downhill slope?

To prevent a car with a manual gearbox from rolling away on a downhill slope, it's important to both engage the parking brake and use the transmission to hold the vehicle. Applying the parking brake physically blocks the wheels and provides a mechanical hold. Engaging first gear or reverse gear uses the engine compression to resist movement, adding extra security. Simply putting the gear lever in neutral is not effective because the car can roll freely without engine resistance, relying solely on the parking brake, which might fail. Combining both methods ensures the car stays stationary and is a safe practice according to German traffic rules.