Guitar Frets are laid out to accomplish an equal tempered division of the octave. Each set of twelve frets represents an octave. The twelfth fret divides the scale length exactly into two halves, and the 24th fret position divides one of those halves in half again. The ratio of the spacing of two consecutive frets is formula_1 (twelfth root of two). In practice, luthiers determine fret positions using the constant 17.817—an approximation to 1/(1-1/formula_1). If the nth fret is a distance x from the bridge, then the distance from the (n+1)th fret to the bridge is x-(x/17.817). Frets are available in
Inlay (guitar) shape for their fret markers to create a brand identity set themselves apart from competitors. Gibson uses isosceles trapezoids while Fender uses dots, but others include lightning bolts, letters and numbers. Smaller dots are also usually inlaid into the upper edge of the fretboard or the neck so as to be more visible to the player who views the instrument from the side. LEDs or optical fiber can be employed to illuminate the markers. This is mostly employed by players who perform in front of live audiences where the lighting is either insufficient or constantly changing. On guitars, there are