I have to jump in here and say something as I am the one who makes the Fiddle Fretter. I was first a guitarist then I took up piano, banjo, mandolin. It was only a few years ago I had a stab at the fiddle. I really just wanted to be able to play a few tunes but I found it painfull to hear those "slightly out of tune notes" (and sometimes not so slightly). I had heard of Fretted fiddles but couldn't find anyone who made them. SO I did a lot of measuring cutting, sawing etc and installed mandolin Frets on my violin. My playing improved dramatically and I was happy with the result. My dear wife looked at what I had done to my violin and said " Why did you hack your fiddle to pieces? Could you not just stick something on that would have the same effect without damaging the instrument? Ah the wisdom of women!
That is when I developed the Fiddle Fretter.
It is not everyone's cup of tea but it effectively frets your violin.
"Permanent" Fretted violins can be obtained from Wood Violins in California.      www.frettedfiddle.com