EMERY BOARD

'Emery boards' are pieces of cardboard which have emery affixed, or have emery paper glued to them, thereby rendering them both coarse and flexible. Therefore, they are widely used by manicurists to shape and smooth the nail after and/or before manicure/pedicure sessions. Because emery boards are made inexpensively to be disposable, they are a sanitary alternative to metal nail files.
The method to smooth and shape the nail accurately is to take light, even strokes in one direction across the top of the nail. Twenty to thirty easy strokes can typically wipe away long fingernails, whereas five to ten strokes are sufficient for simply shaping the nails.
Emery boards are an easy way for baseball pitchers to "scuff" the ball, giving it more grip and movement. This manipulation of the ball is regarded as cheating. In an infamous incident in Major League Baseball, Joe Niekro of the Minnesota Twins was caught with an emery board in his pocket. He was suspended for ten games.