There's lots of different kinds of knife sharpener, all do much the same thing, choice is usually down to personal preference and comfort. One of the most popular and well known knife sharpeners is the Chantry knife sharpener which will sharpen any plain or scalloped edged knife safely and efficiently without wearing away the blade. It does this with its two small butchers' steels which are pre-set at the optimum edge angle and are spring loaded so as not to damage the knife.
Another popular design of knife sharpener, particularly with professional chefs, is the traditional sharpening steel. We stock both the James Martin brand and the Stellar Sabatier, both are excellent knife sharpeners. Our Kitchen Craft knife sharpener has a suction base to keep it attached to a work surface while you work the knife through it.