The truth is that chopping with a dull knife is not only difficult and unsatisfying—it’s also unsafe. A dull knife is far more likely to slip off that red onion and cut you than a well-maintained blade. Not to mention the fact that good knives are expensive and deserve the right care. So yes, it’s time to invest in a knife sharpener, but what kind? There are manual sharpeners, electric sharpeners, sharpening stones, sharpening rods, and more. Below, some great options.