Vault Keyhole Signals quickly signal the status of locks to personnel and outside users with a color-coded system. They are ideal for use at banks, rental facilities or post offices. Made of colorfast, nonchip nylon, the 7/8" prongs securely engage lock tumblers for a tight fit. Offset head centers signal over keyhole opening. The 1/2" head fits most popular lock brands. Signals are scratch-resistant and chip-resistant as well as reusable. The color blue denotes rent overdue while other colors are designated for other signals.