frets

Frets are thin strips of metal embedded into the fingerboard of many stringed instruments to shorten the vibrating length of a string and produce specific pitches. When a string is pressed just behind a fret, the vibrating portion becomes shorter, raising the pitch. On most fretted instruments, the pitch sequence follows a tempered scale that divides the octave into twelve equal semitones.

Frets are usually made from nickel-silver alloy, stainless steel, or brass and are installed as wires either glued into grooves or pressed into the fretboard. In most Western instruments, frets are fixed and immovable. Some instruments, notably certain Indian instruments such as the sitar and sarod, use movable or tied frets that can be adjusted for microtonal intonation and alternate tunings.

The spacing of frets is determined by the instrument’s scale length, with precise positioning required so that each fret corresponds to a half-step interval in equal temperament. Frets wear with use, which can alter intonation and action; when wear becomes pronounced, a repair called a refret may be performed to replace the worn wires.

Variants include zero frets, which act as a consistent nut-like position before the first actual fret, and fretless instruments that rely on finger position without frets. Frets are a defining feature of many common instruments, including guitars, basses, mandolins, and banjos, while other traditions employ different fret systems or movable fretting arrangements.