I am planning on doing a fretless conversion on a bass guitar. Does anybody sell metal "frets" to mark the lines, or pre-made plastic markers I just need to glue in? If not, what is the best material to use as fret markers, how do I glue them in, and how do I file/sand them down flush with the fretboard without damaging the board?

Thanks!

I wouldn't use metal to fill in the gaps left when you removed the existing frets. The reason is that they will wear at a different rate to the wood of your fretboard and will eventually be raised slightly above the wood creating undulations in your board.

I have used wood strips usually sold as guitar binding and glued then into the grooves. You can try to find a wood similar in colour to your existing fretboard or if you want the lines to show up, use a different colour.

The best way to file them is to trim them to near the required height using a very sharp craft knife and then sand your board as you would when finishing it during the making of a board.

I like the wood idea better than the metal or plastic. I know it's possible to buy radiused sanding blocks from Stewmac, but how would I know which one to buy? How do I know what the original radius of my fretboard is?

Well, Stewmac also sells gauges to find the radius. Probably the radius changes as you go up the neck. I think it's easiest to use a flat sanding block that's about six inches long. As long as you sand the whole fingerboard pretty evenly, you should come out about right.

Here is a neat link that might help you ......tom

http://www.mikelull.com/fretless%20conversion/conversion1.htm

Good luck