 Robotic cleaners use fans, vacuum or magnets to stay firmly attached to glass, while cleaning windows on the inside or outside in an “N” or “Z” pattern, squeegeeing them dry as they move on.Window cleaning and window cleaners are the subject of songs, films and comment, often with comic intent.Examples include George Formby's comic song "The Window Cleaner", also known as "When I'm Cleaning Windows" is one of the best known.