This thick steel tool is a measuring device for both wire and metal sheet. B & S is short for Brown and Sharpe (also known as American Standard or American Wire Gauge) and is a universal system for finding the gauge, or thickness, of metal. The larger the number, the thinner the metal. You can usually purchase a B & S gauge from a jewelry supply house, a well-equipped bead store, or from online jewelry tool vendors. If you are in Europe, a British Standard Sheet and Wire gauge is the equivalent tool.