The Janka Hardness Scale refers to a range of numbers that determine the denseness of a particular wood species and its subsequent resistance to dents and dings. The actual number listed is the amount of pounds-force required to embed a .444" steel ball into the wood to half the ball's diameter. Therefore, the higher the number, the harder the species. Keeping the Janka rating in mind can be helpful in choosing a species that aligns with your durability requirements.