Consider the weight, do not overload the roof box. It is important to check the maximim load for your car roof. A good rule of thumb is that a car can handle about 100 kg on the roof, but then you need to deduct about 25 kg for the roof box and roof racks. This leaves about 75 kg for bags and other luggage in the roof box. It’s best to load the heavy luggage in the car and the lighter luggage in the roof box.
Make sure to secure the things you put into the roof box, there is a risk of damage to the box in the case of braking.
Do not load too high, it is easy to damage the roof box if you have to forcefully close it.
Keep in mind that the height of the car increases by about 40-60 cm when driving with a roof box - the stability of the car deteriorates due to this and some garages cannot be driven into with the increased height.
If it is winter, remember to bring some lock spray if the lock freezes.