Beautiful furniture requires accurate joinery, and that accuracy requires square boards which are free of twist. Even small amounts of twist can wreak havoc with forming solid joints. To detect these minute amounts of warpage, a tool is needed. The tool most often employed is the winding stick. Winding sticks are nothing more than a pair of long straight sticks that are laid across each end of a board to amplify any existing twist to the eye.
I made mine out of hickory, because it is a very hard wood with straight grain. Each one is approximately 18 inches long, with a pair of holes on one board to make sighting any twist a bit easier. I also chamfered the tops of each board to remind me that I only need to maintain one side. I finished them with a couple of coats of tongue oil.