The Sharpmaker Tri-Angle knife sharpener allows anyone to effectively sharpen a knife with just a few minutes of practice. The ABS base features slots that allow you to precisely adjust the sharpening angle of the stones to 30° (15° per side) or 40° (20° per side) for sharpening knives. Simply hold the knife blade vertically and run the edge along each sharpening stone. It's that simple. For serrated blades, use the rounded edges of the stones and a slightly wider grip to allow the stone to penetrate the grooves of each serration. The Sharpmaker system includes two sets of high-alumina ceramic stones: a pair of medium-grit (brown) stones for aggressive sharpening and a set of fine-grit (white) stones for a professional finish. A set of aluminum safety rails protects your hands during sharpening, and all components snap into place in the ABS base and cover for easy storage. Every Sharpmaker machine comes with a detailed manual and DVD that guides you step-by-step through the process of sharpening knives, scissors, awls and many other tools.