Emery boards are pieces of cardboard which have emery or emery paper glued to them, making them both abrasive and flexible, used for fingernail and toenail care. They are used by manicurists to shape and smooth the nail during manicure and pedicure sessions. Emery boards are inexpensive and disposable, making them a sanitary alternative to metal nail files. The emery board was first patented by J. Parker Pray of New York in 1883. (source)