cast, turned, brazed or spun from a variety of materials. Levers could be wrought or cast. Designs became more complicated and might include a rose or escutcheon plate. Until about 1830 door handle manufacture in the western world was almost entirely European. In 1838 the USA was importing between 80 and 95% of its door handles. Between 1830 and 1876, the date of the Centennial Exposition, door handle manufacture grew rapidly in the US; more than 100 patents were filed for door handle and door knob improvements in that time. From the early 20th Century architects and designers started to take serious interest in door handles as part of a comprehensive vision of spaces for living. In 1927 Wittgenstein famously designed a door handle which has become a prototype for curved tubular handles since then. Emerson wrote of handles in his "The American Scholar" address. Peter Behrens, Walter Gropius and Antoni Gaudi all produced handle designs, many of which continue to be manufactured. While aesthetic design, cost of manufacture and functionality remain primary drivers of door handle design, the 21st Century has seen additional considerations introduced. In particular, considerations of infection control {see section below} and accessibility have become increasingly important since around 2000. The Coronavirus pandemic has contributed to a rapid development of new handle designs including foot-operated handles and handles that can be operated by the user's forearm. Escutcheon plates Escutcheon plates are the keyhole covers, usually circular, through which keys pass to enter the lock body. If the door handles have a square or rectangular plate on which the handle is mounted this is called the backplate. The backplate can be plain (for use with latches), pierced for keyholes (for use with locks), or pierced and fitted with turn knobs and releases (for use with bathroom locks). The plate on the front edge of the lock where the latch bolt protrudes is called the faceplate. Usage The location of the door handle along the horizontal axis on the door can vary between a few inches or centimeters away from the edge of the door to the exact center of the door, depending on local culture, decorative style, or owner preference. The distance from the edge of the door to the center of the handle is called the backset. The location of the door handle along the vertical axis on the door may vary between . Door knobs