Safe fret crowning was brought to the guitar community in 2011 by inventor Davide Bissoli. The true original V-shaped fret file prevents contact with the very top of the fret—the critical point where the strings make contact. This innovation made fret crowning significantly safer, as it preserves the fret height by avoiding unintentional flattening of the crown.

Crowning with the LittleBone Fret File (also known as the Bissoli Fret File) is performed in a few straightforward steps. The first step removes the bulk of the material from both sides of the fret in a consistent, controlled manner, leaving a clean geometry ready for final rounding and polishing using sandpaper or other fine abrasives.

Over the years, similar-looking tools have appeared on the market. Some of them maintain the same operating principle as the true original protected by patent. Anyone who owns one of these tools can verify this through a simple test:
Use it on small frets—such as those on a mandolin, ukulele, or vintage guitar—while placing a standard fretboard protector over the fingerboard. If the file touches only one side of the fret at a time without scraping the top, it likely operates on the same principle as the true original.

This tool, along with its operating principle and method, is covered by the following patents:
  – USA: US9070347B2
  – Europe: EP2720221B1 (UK, DE, IT)
  – Japan: JP5841597B2