True story:

In the late 1950s, when we were teenagers, my pal Lester and I visited the tool department of a hardware store. Lester was identifying some of the tools for me. Lester's Dad was a machinist, so I was inclined to believe him. He picked up a metal file, and said, "This is a flat bastard." I looked at the label, and sure enough, it was a flat bastard. He picked up another file and said, "This is a round bastard." I checked its label, and he was right again. Damn. Then he picked up a wood rasp, and said, "Now this is a rough sonofabitch."

I'll bet this was an antique joke when Lester's Dad first heard it.

Joe