A nail file is a tool used to gently grind down and shape the edges of nails. They are often used in manicures and pedicures after the nail has been trimmed using appropriate nail clippers. Nail files may either be emery boards, ceramic, glass, crystal, plain metal files or metal files coated with corundum. A nail drill is a powered rotary tool, which is used by a nail technician to file nails. Materials Emery board Emery boards are small flat long objects 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. Emery boards are generally less abrasive than metal nail files, and hence, emery boards may take longer to file down nails than metal nail files. Emery boards are usually less expensive than metal nail files, therefore emery boards can be economically disposed of after use on a single person. The nail can be smoothed and shaped accurately by taking light, even strokes in one direction across the top of the nail. Twenty to thirty easy strokes can typically shorten excessively long fingernails, while five to ten strokes are sufficient for shaping the nails. Guitar players have also been known to use emery boards to smooth out calluses which may snag the strings of their guitars. Emery pitches Baseball pitchers and cricket bowlers have been known to use emery boards to scuff the outside of the ball. The roughness can offer more grip and hand control. Surface scratches also alter the ball's aerodynamics making it more susceptible to spin and movement when in flight. However, the deliberate manipulation of the ball using an emery board is classified as cheating in baseball and cricket. In a 1987 Major League Baseball incident, Joe Niekro of the Minnesota Twins was caught with an emery board in his pocket and suspended for ten games. He claimed it was for filing his nails. Glass Glass nail files are more recently available. Since glass nail files have a smoother and more even surface they do not splinter the nail like emery boards or metal nail files. This makes