why fretboard? Google images seems to prefer fret diagram.

Check https://www.google.fr/search?q="fretboard+diagram"&tbm=isch&tbo=u&source=univ&sa=X&ei=jZtvUpHeC4uY1AXY-YCgCg&ved=0CC0QsAQ&biw=1920&bih=895
https://www.google.fr/search?q="fret+diagram"&tbm=isch&tbo=u&source=univ&sa=X&ei=jZtvUpHeC4uY1AXY-YCgCg&ved=0CC0QsAQ&biw=1920&bih=895