Traveling Tool Kit: Safe Corner Triangular File

I buy the narrowest triangular file I can find. I think this one is called "double extra slim." Then, I grind all three corners safe and slightly rounded, so I can use the file to round frets after I've leveled them. Used in conjunction with the little sheet metal file guard, it's safe and effective, and, for me at least, much more controllable than a regular fret crowning file.
