How do I check the sharpness of my knife?

The concept of sharpness of a knife is directly related to the concept of the cutting edge, which is formed at the intersection of the two planes of its blades. A well-sharpened knife has both blades polished to such an extent that they form a very thin, sharp edge, which must necessarily have a V-shape. The essence of the sharpening process is to remove excess particles from its blades so that the edge becomes V-shaped. The easiest way to do this is to use a special device for sharpening knives. How to check the sharpness of the knife?

Rather well-known and simple is the tomato test. Try to cut a thin slice of a ripe tomato. If it can be done without pressure on the skin, and the juice stays inside, then the knife is sharp.  You can also use paper to check the sharpness of the knife. Holding a sheet of paper in one hand and the knife in the other, try to cut a thin strip of it all the way through. A blunt knife will cut the paper unevenly or not at all. You can also check the sharpness of the knife on the hair of your hand, though you should do it with caution. Move the knife along the arm along the hair against its growth, without touching the skin. A sharp enough knife will cut through all the hairs in its path in one pass, but to achieve this sharpness you can only use the special sharpening abrasives found on knife sharpening systems such as the Hapstone R2, Shapton Pro and others.