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 in (7.9 mm) fiber cement siding. Permits one person application of panels. Two gauges support entire length of panel and precisely gauge a standard 1-1/4 in (31.2 mm) overlap.