If you do not remove enough metal to create a new edge, you will leave some of the dull edge in place. A dull blade (or a blade with dull spots or nicks) will reflect light from the very edge of the blade. A razor sharp knife edge will not show "bright spots" when you hold it blade up under a bright light. You will need to remove enough material from the sides of the bevel so that the edge stops reflecting light.
A diamond plate is a steel plate, sometimes mounted on a plastic or resin base, coated with diamond grit, an abrasive that will grind metal. When they are mounted they are sometimes known as diamond stones. The plate may have a series of holes cut in it that capture the swarf cast off as grinding takes place, and cuts costs by reducing the amount of abrasive surface area on each plate. Diamond plates can serve many purposes including sharpening steel tools, and for maintaining the flatness of man-made waterstones, which can become grooved or hollowed in use. Truing (flattening a stone whose shape has been changed as it wears away) is widely considered essential to the sharpening process but some hand sharpening techniques utilise the high points of a non-true stone. As the only part of a diamond plate to wear away is a very thin coating of grit and adhesive, and in a good diamond plate this wear is minimal due to diamond's hardness, a diamond plate retains its flatness. Rubbing the diamond plate on a whetstone to true (flatten) the whetstone is a modern alternative to more traditional truing methods.
"How do I use this daunting metal rod?" I hear you ask. Well, it's not too hard, really. The best way for a beginner is to balance the steel on a surface with the tip secured by a damp tea towel. You want to get that angle right, whether it's around 15 degrees for a Japanese knife or 20 degrees on a German or French blade. Then swipe slowly down, away from you, making sure the whole blade is honed – around five swipes on each side should do.
Sharpening on the other hand is reupholstering the furniture or telling the hair stylist to give you a new look. Material is going to be removed from the edge of the blade. There’s no way around it. How much is removed will be a function of just how dull the knife has become or whether you’re sharpening to compensate for a chip in the edge or because the tip has broken off. If your knife is not damaged and you have it sharpened twice a year very little material will be removed each time, yet it may still be enough for you to notice just by looking carefully with the naked eye.
Clean the knives and stone. As soon as you've finished sharpening your knives, wash and dry the blades. You should also clean the stone according to the manufacturer's instructions. For example, if you have an oil stone, you might need to scrub it occasionally with a stiff fiber brush and soak it in oil. For a water stone, wash off any of the residue and store it in a dry cloth until you need to use it again.
The type and size of the blade being sharpened determines the size of the stone needed. In general , a 6" stone is considered a small sharpening stone, an 8" stone is a common larger size, and a stone larger than 8" (10"-12" are available) is considered generously sized. Stones smaller than 6" (3" and 4" stones are quite common), are considered pocket stones and can be used for toolboxes, tackle boxes and on-the-go sharpening, but are generally not recommended for regular sharpening jobs.
Over the course of two days I re-sharpened nearly a dozen old blades, including removing the secondary bevel on an old stainless Ontario saber-grind Navy diver's knife, convexing the edge on flat ground 1095 Schrade 55 that also came with a secondary bevel, and fixing a broken tip on an old Kershaw folder. These stones made quick work of the Schrade and Kershaw. Both had completely new edge geometry within 30 minutes apiece. The Kershaw looked like-new, as if the tip had never broken. And the Schrade cut much better than it's secondary bevel would previously allow, regardless of how sharp I got it with a ceramic rod and strops. The Ontario took a little more work, as it had been abused a little the last time I'd held it, over 25 years ago and was as dull as a case knife - one of the reasons I decided to go ahead and do a full saber grind - well, a slightly convexed saber, I suppose would be more accurate. But within under an hour of using the two stones and a couple leather strops (one with black compound, another with green), the Ontario was shaving sharp again too.
I recommend it as a lightweight alternative to larger stone for smaller knives. Leather necklace is comfortable and seems strong. I conditioned it for suppleness and swim with it on tightened as a choker. Stone is small, dog-tag size. I use it with water. Functional for small folder knives and multi-tools. Not useful for large fixed blades, since you can't make a long stroke. Small to grip. I use double-sided tape on one side to keep it in place on a flat rock. Not sure of grit, seems like around 1000. It took a while, but i got my old boy scout knife sharp.