Jammed the side of a blade (by the spine) against a small nut to hold it while I unscrewed the bolt. Didn't have any thing else to grip it with.
It was a DLC Para 2, and the wee nut turned a couple of faces before I got it to loosen. That DLC is a mean coating, it wasn't noticeably scratched at all.
OK not really hard use, but hard on the blade coating.