One factor in keeping stock flat and true after you mill it is knowing its moisture content before you surface it. General Tools’ Non-invasive Moisture Meter ($90) makes it easy to check 3/4" stock: Set the device on a board, hit the “Measure” button and then calibrate the gauge from a chart of 50 different wood types. The meter sends an electromagnetic signal into the material and beeps you back with a readout in seconds. No more wondering about wood wetness. General also provides calibrations for testing plywood, paper, drywall and several fabrics.