Fret
A fret is a thin strip of varying materials (most commonly metal, but occasionally gut or nylon) found on string instruments. Guitars, mandolins, and banjos have frets.
Frets are mounted on the long necks of the instrument. The frets help the musician playing the instrument to know where to place their fingers on the instrument.
On historical instruments and some non-European instruments, pieces of string tied around the neck are frets.
Frets divide the neck into sections related to a musical framework. On instruments such as guitars, each fret marks one semitone in the standard western system where one octave is divided into twelve semitones.
Fret Media
The neck of a guitar showing the nut (in the background, coloured white) and first four frets
Frets tied on to the neck of a saz; note microtonal frets between semitones.
Other websites
Media related to Frets at Wikimedia Commons