Winding sticks provide a time-honored way to check the flatness of workpieces or assemblies. Used in pairs, winding sticks are placed parallel to each other at opposite ends of, for example, a board being hand-planed. To check for twist, or “wind,” crouch so that your eyes are level with the top edges of the sticks, and then sight across them with both eyes open. Any deviation in the flatness of the surface will be immediately apparent.
Traditionally, winding sticks are made from straight-grained, identically sized pieces of hardwood–often of strongly contrasting colors for easy sighting. The problem with wood is that it can warp over time, requiring occasional redressing. Instead, I use aluminum angle from my local home supply store. (For straightness and rigidity, get the 1⁄8"-thick stock.) To provide contrast, crown one with black electrical tape.
Will Murphy, San Francisco, California