The best knife sharpeners – and how to use them A knife is arguably the most important tool in the kitchen, but it's essential that the blade is sharp. When blunt, you have less control and are more likely to see the knife slide off the food, thereby making cooking a more hazardous process. You've acquired a chef's knife, you're using it almost daily to make tasty dinners for the family, and it's stored in a nice knife rack or a magnet for safekeeping. So why stop there? Keeping that knife's edge fine will make cooking not only safer but, let's face it, much more fun. Whether you've spent £150 on a high-end knife or under a tenner on a dinky paring knife, keeping it sharp is crucial.