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A good thing about the cardboard type of fingernail file is that you can take the scissors and trim the point to fit into tight places. Mack

Shutterbug
That would work but needle files tend to be a little thick to get into small spaces. That is why I use finger nail files. I use it on making pocket knives and it works great. Mack

Finger nail file. The metal type with grit on them. I grind the grit off and then glue on a strip of sand paper. Then scrape it off and glue on the next finer grit. You can also use the cardboard...