Every once in a while you'll see a reference to somebody being "on tenterhooks"-that is, a state of extreme uncertainty. When I saw that this morning I asked myself "What in the hell is a tenterhook, anyway?"
Well, it's a sharply hooked nail that is used to stretch wet cloth over a frame so that it dries flat. A person whose job it was to put the combination of tenterhooks and wet wool over a frame was known as a tenterer-as are the workers in the picture.
The fine folks at the Trowbridge Museum have put together a website that provides much detail on the various now forgotten trades associated with cloth making. It's well worth your time to have a look.