The Gecko Gauge SA903 gauges and supports cement-board siding for one-person installation with virtually no layout time. It is adjustable at 1/4 in. increments for 4 in. - 8 in. siding reveals. It won’t scratch or mar pre-painted siding. The Friction-Cam mechanism supports full 12 ft. cement-board siding lengths. It can be used with 5/16 in. fiber-cement siding products, including James Hardie’s updated HZ5 series with new “eased” drip-edge profile. ONE-PERSON INSTALLATION - Working as a pair, the gecko gauge fiber cement siding tool supports fiber cement siding for one-person installation with virtually no layout time.USE WITH FIBER-CEMENT SIDING - Use the SA903 gecko gauge siding tool with 5/16 in. fiber-cement siding, including James Hardie’s updated HZ5 series.ADJUSTABLE - Each gauge is adjustable at 1/4 in. increments for 4 in. - 8 in. siding reveals.PATENTED FRICTION-CAM MECHANISM - Supports full 12 ft. fiber cement siding lengths.WON’T SCRATCH OR MAR - Heavy gauge plastic won’t scratch or mar pre-painted siding.