Precision StraightedgesOur Precision Straightedges are specifically designed for accurately checking neck straightness and relief, evaluating truss rod adjustments, and identifying high or low frets on any fretted instrument, ranging from mandolins to guitars and basses. They serve the purpose of precise fretting and neck evaluation. These straightedges come in four different lengths: 12" x 1. 5" x 0. 079" (304mm x 38. 1mm x 2mm) 18" x 1. 5" x 0. 079" (457mm x 38. 1mm x