A bread knife generally has a sharp edge that has saw-like notches or teeth, which is referred to as a serrated edge. The blade of a bread knife is 8 to 10 inches long. 8 inches is a common length used for a bread knife. The knife's long serrated blade works well to slice through food that is hard on the outside and soft on the inside, such as slicing through the hard crusts of bread. The serrated-edged knives are difficult to sharpen so many times a new knife is bought rather than trying to sharpening a dull serrated blade.