Just a regular ol' sharpening stone about 2 x 8 inches with a med grit on one side and fine on the other.
I had one significantly high fret in this neck, and I didn't even look for others yet because I could find this one without even a fret rocker. Went over the whole board with a few passes of the rock & voila! Didn't have to touch another fret.
I've never used a file, so maybe it's just as easy, but the rock seems foolproof. (Just don't make too many passes.)
Ummm, yeah, cuz last I checked, they still had not come up with a board stretcher/thickener
True, but I saved Neck One. As a side project, I plan to pull the frets and route a flat edge on both sides. Then laminate some maple to it. Reshape, reslot, and refret. The appearance should be like a binding. Hopefully.
I might be able to use it on my next project... Here's a pic of the inspiration for the body shape

This is actually the body of a Washburn guitar. I have some carving ideas from a "Solace" brand guitar in a nearby shop. Hopefully I will advance my skills as I have not done a carved top yet. Will still be a bolt on neck. I'm still prone to "things happening" so I don't have the confidence to go for a set neck yet. Maybe #3 :)
...so ever since then, I always hang on to the buckle.