Sharp Corners

If you have a sharp corner on a harmonica that's bothering you, get a file and get rid of it. Sharp corners can be a byproduct of the punching process on metal pieces or from the injection mold process with plastic pieces. Either way, there's plenty of underlying material to get out a fine file and take that sharp corner down. Sometimes just a basic emery board for finger nail care can do the job. Make sure to point the holes of your harmonica down so that any particles that come off don't go into your harmonica.