A toolbox full of gauges

When you need a gauge to check diameters on a turning project, you don't ordinarily reach for a wrench. But open-end wrenches make handy gauges for checking small diameters because, unlike calipers, there's no need for setting and resetting the jaws. For example, have ⁵⁄₈ ", ¹⁄₂ ", ³⁄₈ ", and ¹⁄₄ " wrenches ready for gauging the diameters when you're turning a finial or tenon. Lightly touch the wrench to the turning. When the wrench slides easily over the workpiece, you've reached the desired diameter.
—from the WOOD® shop