The protective film of installed security door must be torn off within a month, otherwise it is difficult to tear. If the film has remained over a month, you can find a place where the film has already cocked and coat some essential balm where the film meets the door, then peel it a little, and coat the essential balm and peel. After several times, it will be easier to peel, so be patient!
There are many ways: 1: If the area is small, you can dip it in banana oil, and then wipe with a clean cloth. 2: Textile industry detergent (bottled one is called A1) can be used to remove it. I have tried the method with good result. 3: Dip it in the mixtue of sulfuric acid and water (or it will cause erosion), and rub with a clean ball after that. 4: Blow it with electric hair dryer, and then tear or remove with a wooden shovel. Solvent oil can be used to remove glue traces.
