Because the lifting feet on the Hercules push straight down on the step with a vertical thrust (see picture on right), it can climb any type of step surface. You can climb waxed wood and wet tile.  The Hercules can even climb a Teflon step. Teflon is the slipperiest substance made by man.  This is because you never know what kind of surface you may encounter when using the Hercules Stairclimber.