Question: what are dots on guitar fretboard for?
Answer: Marker dots (see Inlay (guitar)) on the face of the fretboard of modern guitars are usually placed at frets 3, 5, 7, 9, 12 (double dot to indicate the octave), 15, 17, 19, 21, 24 (double dot to indicate the second octave). ... Typically, up to 24 frets are used.