A hardness test, usually for wood flooring, the rating is pounds of pressure required to press a steel ball .444 inches in diameter one half way into the wood. It is one of the best measures of the ability of a wood species to withstand denting and wear. It is also a good indicator of how hard or easy a species is to saw or nail. Northern Red Oak, for example, has a Janka hardness rating of 1290. Brazilian cherry, with a rating of 2350, is nearly twice as hard.