Strong, 1-piece, tempered spring steel construction. Precision ground tip assures gauge will grip behind siding plank. Works with 5/16" (7.94mm) fiber cement siding. 1 person application. 2 gauges support entire length of plank and precisely gauge a standard 1-1/4" (31.75mm) overlap in 1 easy step. No adjustments to vary and nothing to mark. Will not mar finish of prepainted siding.