The Janka hardness test measures the force required to embed a .444 inch steel ball to half its diameter in wood. It is one of the best measures of the ability of a wood species to withstand denting and wear. By the same token, 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.