New 13+ String Action Gauge Electric Guitar. They're easy to use and give clear readings in inches or. Perfect for obtaining accurate action measurements for electric guitar, bass and acoustic guitar 2. A guitar action gauge is a custom ruler designed for measuring action on the guitar. A string action gauge isn't the only way to measure string height, but it sure makes life a lot easier. String Action Gauge Electric Guitar - Acoustic Electric Guitar String Action Gauge Setup In Mm Ruler Steel Luthier Tool For Guitar Bass Tool Mart Tool Rulerstring Power Aliexpress The string height markings are at increments of.