Using the wrong type of knife (or a badly designed one), not only makes it difficult to slice your bread, but it also ruins your crumb (the fluffiness on the inside of your bread).
A knife with scalloped serrations doesn’t dig in and grab the crust as easily, even though it does cut horizontally. This makes it less suited to crusty bread than the pointed serration style.
Most bread knives will be between 7 and 10 inches long give or take a few. But in the case of a knife for slicing crusty bread; the longer the blade, the better.
A blade that is thin, with a narrow angled bevel performs better with crusty bread. The bevel is the angled edge of the blade that has been sharpened and angled towards the cutting surface.