This gauge shows the exact width and depth of sizes 0, 10 and 20 biscuits slots, allowing you to determine which biscuit size will fit before cutting (and potentially blowing out an edge). Once correctly positioned, the pencil slots allow you to perfectly center your marks. Gauge shows actual cut, which accomodate the swelling of the biscuit once glue is applied. Hole allows it to be hung on the wall.