I have a set of decent precision files which I used to use for (among other things) minor fret edge refinements. However, one day, despite masking off the fretboard, I had one of these files jump off the edge of a fret, cut through the mask, and carve a 7mm scratch into the fretboard. Luckily it doesn't affect play, but you can imagine how annoyed I was at myself. I looked around and discovered that Thomann now sell a fret file - so on a punt I ordered one. Wow, it is so much easier to work with than a precision file! Because the abrasive edge is concave to the edges of the file and the rest is flat metal, you only risk wearing down the fretboard at points where the frets meet, and that is easily mitigated by masking. While I'm sure a profession luthier will point out why their expensive fret file might be better than this, I'm only using mine intermittently so it's more appropriate for purposes. I wish I had got one of these sooner.