Magnetic strips will only hold to non-aluminum metal.  A small % of vehicles have aluminum or fiberglass/carbon fiber body parts.  If you’re unsure, we suggest the refrigerator-magnet test on your vehicle. For non-magnetic surfaces, we have the suction-cup door guard available. These are heavy-duty rubber suction cups that are pushed onto the vehicle for a firm seal and quickly hand-tightened for a lasting hold.