I tried to do this once, but despite some (small amount of) hand filing experience at the time, I was not able to produce a working key before getting bored and

I tried to do this once, but despite some (small amount of) hand filing experience at the time, I was not able to produce a working key before getting bored and giving up. I even had an existing worn key to try and copy. I reckon I could do it now (but for that matter I also reckoned I could do it then). I would not back the average person's chances. It's harder than it looks.