Strings of a violin (or any other stringed instrument) are held in tune because of the tension on the peg going into the peg box. When the pegs do not fit tightly into the peg box, the strings can slip, causing the instrument to go out of tune. This is particularly a problem on newer instruments. Peg Dope is a product that can be applied to the tip of the peg, creating additional friction which then stops the strings from slipping.
