Naniwa S2 430 Super Stone 3000 Grit Japanese Whetstone Knife Sharpener Lynn Thompson designed it to Lynn Thompson designed it to concentrate the full force of a crushing blow in a small area so that even a moderately powerful blow can be remarkably effective in disarming or otherwise incapacitating an attacker The blade is supported by a highly refined back lock mechanism that takes this time tested lock design and elevates it to a new standard of engineering and manufacturing excellence making them more durable and effective than other makes Instructions: Splash stone with water before sharpening and continue to do so when sharpening