Over time Whetstones can develop grooves where the stone has worn away, this makes for uneven contact on Knives/Chisels.

This Flattening Whetstone maintains your Sharpening Whetstone by flattening out any grooves to ensure the best contact with the sharp edge of your Knives/Chisels.

Now if only a whetstone could be developed to maintain this whetstone.......the cycle continues.....