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
Romantic guitar mainly used for plucking with, in the 19th century, a free stroke ("tirando") more commonly than the rest stroke ("apoyando") that was favoured in the 20th century. Unlike most classical guitarists today, players were divided as to whether or not use fingernails. Fernando Sor, for example, did not use them while his compatriot Dionisio Aguado did. The narrower fretboard of the romantic guitar allowed the left-hand thumb to be used by some guitarists to fret the sixth string although Fernando Sor deprecates this in his method, recommending that the left-hand thumb remain at the rear centre of the neck and