Inch and metric versions now available! Our String Action Gauge is a "Swiss Army Ruler" for setup adjustments on any stringed instrument. This pocket-size stainless steel rule has become a luthier's favorite in busy shops. It's the best way yet to get vital measurements on acoustic and electric instruments. String height Bridge saddle height Saddle slot depth Fret slot depth (unbound fingerboards) Nut height Pickup polepiece height See details below