What is foil on doorknob why?

Foil is sometimes used on doorknobs as a deterrent to prevent someone from touching or turning the knob. This method is often used in hospitals or other medical settings to reduce the spread of germs and infections. The foil acts as a barrier between the doorknob and the user's hand, which helps to prevent the transfer of bacteria. Additionally, the foil may be used as a safety measure to prevent static electricity from building up on the doorknob, which can be dangerous in certain situations. While foil on doorknobs may not be a common practice in residential settings, it is often seen in public spaces where hygiene and safety are a priority.