The Dressing stone is a great little tool to clean and refresh your Whetstones during a sharpening session. As you sharpen, removed metal will build up on the stones surface. If not removed, the metal build up can slow down your sharpening process considerably. It also generates a thin layer of mud on finer types of stones that gives a nice polishing effect during the sharpening process.
The Dressing stone needs to be soaked for at least 10min before use.