Made in Japan.
Flattening your water stones is an important process for maintaining them so that they give optimal performance. This Naniwa Flattening stone is designed to work with Naniwa Water Stones but we've found it works well on any waterstone.
Soak the flattening stone before use, and soak or wet the water stone as appropriate. Place the water stone on your work surface or hold it in your hand and then rub the Naniwa Flattening Stone over it until the water stone is perfectly flat.