Rhino Rulers were developed by a contractor working "hands on" in the field. Wooden spacing folding rulers he used simply did not stand up to the extreme weather conditions he faced. They would warp, the paint would peel off and worst of all, they would break very easily. Through extensive research and field testing, the final product is a waterproof folding ruler that can take as much abuse from the elements as you do. EngineerSupply is a Factory Authorized RhinoTools Dealer.