Magnetic card as they are likely to know many of the RTL II program "Grip". You put the magnetic card on the car to the body and you can feel a significant attraction of the magnet to the metal body. If a fender has been leveled after an accident, so he attraction is significantly reduced or no longer present. Thus repaired accident damage can be easily, quickly and inexpensively detect. Only works with auto parts made of metal which are also magnetically (no aluminum, carbon, etc.).
