<P> 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 . </P> <P> Emery boards are small flat 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 . </P> <P> Emery boards are generally less abrasive than the metal nail files, and hence, emery boards may take longer to file down nails than metal nail files . However, nail files may play a role in disease transmission if they are used on more than one person without adequate sterilization . 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 . </P>

What are the two sides of an emery board for