Gauges and supports siding for one-person installation with virtually no layout time. Adjustable at 1/4" increments for 4"-8" siding reveals. Won't scratch or mar pre-painted siding. Friction-Cam mechanism supports full 12' cement-board siding lengths. For use with 5/16" fiber-cement siding products, including James Hardie's updated HZ5 series with new "eased" drip-edge profile. Made in America.