The Lansky Controlled-Angle Sharpening System is a guided knife sharpening system that ensures your knife gets sharpened to the exact bevel you specify every time. This system is designed to give your blade a professional, razor sharp edge 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. The Lansky Controlled-Angle Sharpening System allows the user to select the sharpening angles that are best suited for their knife's intended use. The four sharpening angles and their uses are listed below: 17? Angle - A severe angle recommended for razor blades, fillet knives or similar tools.