During the maintenance process, it is often encountered that the screws cannot be unscrewed, or even the hexagonal or external hexagonal screws become damaged but still cannot be unscrewed. What should be done then? Here are several simple solutions:  1. Drip some diesel or kerosene or spray some loosening agent beforehand.  2. Use a hammer to strike the head of the screw, without damaging the hexagon or internal hexagon. Try to use an internal hexagon wrench or Plum blossom wrench and a socket wrench， and use the socket wrench to hit the hexagonal screw.  3. If the screw is damaged or has a problem， weld another screw to it to unscrew it.  4. For screws that cannot be unscrewed in the recessed holes of household plastic electrical appliances， use an electric soldering iron to heat the screw for a while， and then use a cross-head screwdriver to loosen it.