In reply to:

---

What kind of file and what kind of technique are used to file in a rear sight on a double rifle?

---

Someone with great technique could most likely use just about any file. (cept for a rattail or chainsaw file)

Someone with a great file but little technique should not even attempt this job!

The most important thing to remember is that it ain't hard to take metal off the sight but it sure ain't easy to put metal back!

Hasten slowly on this one.