If possible, place the heavy objects in the middle of your roof-box, so that the overall payload will be distributed evenly over the load-bearing rack and the car. All packed articles must be securely tied down to prevent slipping. It is important to ensure, that the load does not present any obstruction to closing the roof-box, in order to prevent malfunction of the locking system. Never exceed the maximum roof load specified by the manufacturer. The maximum overall weight ("gross vehicle weight") of your car must not be exceeded.