When choosing wire, the "gauge" is the diameter or thickness of a wire. When steel wire was first measured, it was determined by how many times it was drawn through a series of dies of progressively smaller diameters. If you want a 9-gauge wire, you'll need to pull it through 9 successively smaller dies; for a 14-gauge wire, you'll need to go through 14 successively smaller dies. In order to strictly adhere to gauge standards, the diameter of wire is now measured with cutting-edge instruments.