Strong, One-Piece Tempered Spring Steel Construction With Precision-Ground Tip Assures Gauge Will Grip Behind Siding Plank. No Adjustments To Vary And Nothing To Mark. Will Not Mar Finish Of Pre-Painted Siding. Works With 5/16" (7.9 Mm) Fiber Cement Siding. Permits 1-Person Application Of Panels. Two Gauges Support Entire Length Of Panel And Precisely Gauge A Standard 1-1/4 Inches (31.2 Mm) Overlap.