What is foil around door knobs?

Foil around door knobs is often used as a burglary prevention method. It is believed that wrapping a door knob with aluminum foil can prevent a person from unlocking the door from the outside. The foil acts as a barrier between the lock and key, making it difficult to turn the key. This method is not foolproof and can be bypassed by professional burglars. It is always best to use more secure methods of preventing burglary, such as high-quality locks and security systems.