Medieval people typically used a whetstone to sharpen their knives for use either in cooking or in their craft. Whetstones were not necessarily used by an individual looking for superior quality, but were instead used mostly as a convenient tool for a quick sharpening. This is exemplified by the hole present near the top of the whetstone through which craftsmen could string some sort of cord to tie the whetstone to their clothing, which makes carrying this tool relatively simple. The guilds of London likely used whetstones regularly, as many crafts such as curriers or cooks relied on the rigorous use of blades, which could thus become dull and unusable. However, using a whetstone to finish a freshly made blade was considered inappropriate, as it would not provide the same edge as a proper grindstone would. The grindstone was a much larger instrument, capable of sharpening a blade much more quickly and effectively than a whetstone because of the speed at which one could use it. It was used more in the initial crafting of a blade, but the whetstone was used for regular upkeep. As mentioned, some crafts were displeased with the use of whetstones to finish their products. The Bladesmiths, for instance, of fifteenth-century London were particularly careful about ensuring that their blades were not ruined by others using a whetstone rather than a grindstone. They raised an official complaint about this issue at one point, which suggests that the people in charge of ensuring the sharpness of their blades were slacking off. 
I purchased this set together with the 400/1000 grit stone assuming that some of my knives were quite dull and would need work on a coarse grit stone. Premium Whetstone Sharpening Stone 2 Side Grit 400/1000 | Knife Sharpener Waterstone with NonSlip Rubber Base & Flattening Stone. This is my first wetstone. First off I tried to sharpen my Chicago Cutlery boning knife. This knife is nearly thirty years old, has been abused in may ways and was quite dull. It was very difficult for me to get a burr on this blade, which I attribute to poor technique. Next I moved on to my Henckels Professional S paring and chef's knives. The paring knife was moderately sharp and was modestly improved after working over all three grits of stone. It would cut paper but again it was difficult to develop a burr with this blade. Undaunted I switched to the chef's knife. This knife is twenty years old and has never been professionally re-sharpened. I have sharpened it twice with a Lanksey sharpening system which marred the finish but did put a good edge on the blade. Lansky Standard Coarse Sharpening System with Fine Hones. The chef's knife was moderately dull and had several pits visible on the cutting surface. I modified my technique for passing the knife over the stone and worked the chef's knife over the 400 grit stone aggressively and eventually I was able to get a burr to form from the tip of the knife all the way to the handle. From there it was a simple process of reforming the burr on the 1000 grit stone and then finishing on the 6000. After sharpening, the chef's knife easily and cleanly slices a tomato with very light pressure and is in my opinion very sharp. Not sushi knife sharp but more than enough for the chopping and slicing I expect of it. I'm looking forward to going back and working both the boning knife and the paring knife over again. Don't expect a good result from this product the first time you use it. Watch videos on using a wetstone, expect to spend at least twenty minutes per knife at first, and practice forming a burr. If you can form a burr, you will be able to successfully sharpen your knife.
You’ve probably seen a number – say 1000 – on the side or top of the Whetstone you just bought and are at a loss as to what it all means, or even worse the person who sold it to you, didn’t know or forgot to mention it. Which ever of these scenarios sounds about right, you are left with a stone and no idea how you should be using it, well let me enlighten you dear reader.
A particularly odd use for the whetstone was as a tool for punishment. There are accounts of people who were found guilty of lying and were sentenced to have their head and hands stuck in a pillory with a whetstone around their neck. The origin of this practice is unknown. Such was the case for William Blackeney, who was discovered to be lying about being a pilgrim, a crime because he was coercing people into giving him gifts and other benefits. After being presented to the city officials, he was sentenced to be publicly shamed via the pillory and was forced to wear a whetstone around his neck for having deceived people for several years. Another case of this type was seen in William Hughlot’s punishment for assaulting several people, one of whom was an alderman. Upon his arrest, he proclaimed that the blame should be on the mayor and he proceeded to insult the court. Instead of the traditional punishment of cutting off the hand of a man who assaulted an alderman, he was pardoned and was given the lesser punishment of imprisonment along with being locked in the pillory with a whetstone around his neck. This use of the whetstone is curious, but when considering the duration of an individual’s punishment via the pillory, probably about an hour or more a day, it would seem that this could be an irritating and shameful punishment.
Whetstones may be natural or artificial stones. Artificial stones usually come in the form of a bonded abrasive composed of a ceramic such as silicon carbide (carborundum) or of aluminium oxide (corundum). Bonded abrasives provide a faster cutting action than natural stones. They are commonly available as a double-sided block with a coarse grit on one side and a fine grit on the other enabling one stone to satisfy the basic requirements of sharpening. Some shapes are designed for specific purposes such as sharpening scythes, drills or serrations.[9]
The stone should be durable: avoid knockoff models that are chipped or cracked. This is a serious concern when purchasing online, especially overseas. A quality whetstone should last a lifetime, and the price offered is a steal compared to the value. You may never have to replace expensive blades if you can simply sharpen a dull edge, and the stone pays for itself after only a few uses.
The more you use the sharpening stone; the edges of each particle within the stone tend to become slightly rounded over time. When you notice that it is taking much longer to hone blades and edges, it means you need to replace the stone with a new one. Sharpening stones come with decks that make it convenient to keep the tool in balance on the stone.