strings ride over the nut into the pegbox, where they wind around the tuning pegs. Strings (which are usually flatwound) usually have a colored "silk" wrapping at both ends for identification and to provide friction against the pegs, as well as protect the windings. The peg shafts are shaved to a standard taper, their pegbox holes being reamed to the same taper, allowing the friction to be increased or decreased by the violinist applying appropriate pressure along the axis of the peg while turning it. Various brands of peg compound or peg dope help keep the pegs from sticking or slipping. Peg drops are marketed for slipping pegs. Pegs may be made of ebony, rosewood, boxwood, or other woods, either for reasons of economy or to minimize wear on the peg holes by using a softer wood for the pegs. Attempts have been made to market violins with machine tuners, but they have not been generally adopted primarily because earlier designs required irreversible physical modification of the pegbox, making violinists reluctant to fit them to classical instruments, and they added weight at the scroll. Early examples included large geared pegs that required much larger holes and/or bracing bars and additional holes, and tuning machines resembling those on a double bass, with metal plates screwed to the sides of the pegbox. Recent advances in machining technology have allowed the creation of several types of internally geared pegs the same size as the usual wooden pegs, requiring no more modification than would be seen in any peg replacement. Bow The bow consists of a stick with a ribbon of horsehair strung between the tip and frog (or nut, or heel) at opposite ends. At the frog end, a screw adjuster tightens or loosens the hair. The frog may be decorated with two eyes made of shell, with or without surrounding metal rings. A flat slide usually made of ebony and shell covers the mortise where the hair is held by its wedge. A metal ferrule holds the hair-spreading wedge and the shell slide in place. Just forward of the frog, a leather grip or thumb cushion protects the stick and provides grip for the violinist's hand. Forward of the leather, a winding serves a similar purpose, as well as affecting the balance of the bow. The winding may be wire, silk, or whalebone (now imitated by alternating strips of yellow and black