There are essentially 2 kinds of Sharpening steels. The traditional metal steel and diamond steels. A traditional metal steel aligns the edge of a knife and is good for maintaining knives that are in reasonably good shape. Sharpening steels should be used frequently and the most important detail that should be observed when using sharpening steel is maintaining a consistent angle. A diamond steel is essentially a sharpening stick . Instead of using metal to realign an edge; a diamond steel uses and abrasive grit to cut a new edge into a knife. They work very well when knives are dull but overuse can take unnecessary metal off your knife or change its shape.