A: When it comes to the best knife sharpeners used in a domestic setting the abrasives used to sharpen the blade should last for quite a few years. When they do eventually wear out many of the best manufacturers will refurbish them for you, typically for a nominal fee. Again, however, unless you are using the sharpener on a daily basis (and there is virtually no reason the average person would do this), the sharpener should last for many years before ever needing service.
Serrated blades have a grind on one side of the blade. Only sharpen the grind side of the blade. Hold the sharpener at the angle that matches the original edge angle. Hold the knife with the edge away from you and the serrated side of the edge facing up. Set the tapered diamond sharpener in a serration so that you fill the indentation. Draw the sharpener towards the edge.
Now you may wonder, if a finer stone produces a better cutting edge why do I need a coarse stone at all? The answer is that finer stones work much more slowly than coarse ones. The amount of metal a fine stone removes with each pass is much less than what a coarse stone removes. If you have an edge with a good shape to it from a coarse stone, this is not a problem because the fine stone doesn’t have to remove much metal to improve the edge. If the edge is dull, it will take many times longer to reshape it with a fine stone than it would with a coarse one.