Angle constancy is the most critical and the most elusive element of hand sharpening. The Lansky Controlled-Angle System is a guided knife sharpening system that ensures that your knife edge sharpens to the exact bevel you specify. Designed to give your blade a professional, razor sharp edge every time, regardless of your sharpening ability. Excellent for beginners and advanced users alike. The original and legendary Controlled-Angle System is the ultimate in Knife Sharpening technology.