In this Part the following expressions shall have the following meanings—

• “diagonal length”, in relation to a relevant area, means the length of a line drawn diagonally across the square enclosing the area (so that the extent of the relevant area is thereby delimited);

• “relevant area”, in relation to a registration plate, means the area contained in a square described on the ground—

  1. a

     in front of the vehicle in the case of a plate fixed on the front of the vehicle, and

  2. b

     behind the vehicle in the case of a plate fixed on the rear of the vehicle,

  where one corner of the square is immediately below the middle of the plate and the diagonal of the square from that corner is parallel to the longitudinal axis of the vehicle;

• F1...