[quote name='anzoid' timestamp='1444640056' post='2884626']
If it's a de-fret - i.e. where someone has at some point taken the frets off an "ordinary" bass, then make sure that whatever they've used to fill the gaps is level with the rest of the fingerboard. Best thing is that the gaps are filled with wood - which should (hopefully, all being well, etc) move with any other shifts in the fingerboard. Some people use plastic wood filer and, personally, I'm not a fan. Also, having wasted time on a buying a de-fretted bass - make sure a good job has been done and that where the frets have been taken out no (or very little) fingerboard wood has gone (and been filled...). The tangs of the frets sometimes rip the wood if the job wasn't done well and if nothing else it's plain ugly.
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All of this! I've done a few defrets, being predominantly a fretless player myself. Don't just assume a factory fretless will be right, though.
I got a Squier VM Jazz FL a couple of years back, just for the experiment you understand! A decent enough piece of kit in general, but the fingerboard was crap! Every fret line was in its own dip. I had to sand the whole fingerboard to make it usable. Sold it on in far better fettle than I bought it. :-)