The Janka Scale indicates the relative hardness of a wood species. The scale was created by measuring the force required to insert a .444 inch steel ball to half of its diameter into a piece of wood. This scale allows you to see how resistant each wood type is to dings and scratches. In other words, how will it hold up to the daily abuse and wear and tear of the kids and the dog going up and down the stairs. The scale also indicates how difficult each wood is to cut and drill, something to keep in mind if you’re doing the craftsmanship yourself.