Box of wards

In the Middle Ages, when locks were mounted to the inside of the door and the locking mechanisms were not covered, the need for more secure locks grew. One protective device was a box of wards, which prevented keys of the wrong shape from being used in the lock. The first wards were created by combining one, two, or three forged metal strips over one another, but over time more complex ward systems evolved with several wards of various shapes arranged in a box over the keyhole. A specially shaped pin provided an additional level of security. The cross-section of the hollow key shank, which had to align with the centring pin in the lock, was fashioned into trefoils, quatrefoils, crosses, or stars. Boxes of wards and the production of ward keys was, and remains, a matter for master craftsmen; up until the end of the nineteenth century, the master locksmith exam included producing a masterpiece lock solely with hand tools.