There are several ways to grind the edge of a knife, such as a convex grind, a hollow or concave grind and a straight or V grind. The convex grind is best in application where heavy materials like wood need to be cut with a great deal of force. The cutting edge is supported by a thick edge of steel. The hollow grind is the opposite of the convex. In this grind the side of the knife is hollowed out along the edge forming a concave shape. This grind is best suited for cutting softer materials like food, where the blade cuts deeply. As the convex edge begins to wear, it becomes more difficult to sharpen. The hollow grind, however, stays at relatively the same thickness through many sharpening. The straight grind or V wedge is a compromise between the convex and hollow grinds.

Blade Grinds

Hollow
For a hollow grind, two concave scoops make the edge. If done right, this leaves the edge extremely thin and sharp, for exceptionally good slicing ability. This type of edge works best when high-performance cutting is needed. It is less suitable for chopping tasks, because the same thinness that gives the edge such great slicing performance also makes this format more prone to chipping or rolling during high-impact activities. That makes this edge especially good for chores that emphasize cutting over impact uses.
Convex
This grind has the sides of the blade arcing down in a convex curve to the edge. The edge on this format is often very sharp, because the convex curves run all the way to the edge without a secondary bevel. It is also a strong edge format, because the thin edge thickens quickly enough to have plenty of metal behind it. The main drawback of this format is that it is extraordinarily difficult to re-sharpen. Knifemakers today tend to use a slack-belt grinder to apply this edge format. You can sharpen the edge in a normal beveled manner, but then you'll end up with just a regular beveled edge that thickens quickly, a format that will be strong but won't be the best cutting format.
Flat
The flat grind is a format that combines most of the cutting ability of the hollow grind, with most of the strength of a saber grind. Flat bevels run all the way from spine to the edge bevels. This can leave the edge thin for high-performance. However, the edge thickens linearly as it moves up, so it ends up stronger than a hollow grind. This grind is also expensive to make, as the maker is required to remove a lot of metal. The combination of cutting ability and strength makes this a great all-around grind. From kitchen knives (which require thin, hi-performance cutting edges) to cooks (which require strong, shearing edges), and all uses in between, the flat grind is often an excellent choice.

Saber
The saber grind has flat edge bevels that normally start around the middle of the blade, and run to the edge bevel. The kabar and many other military knives show this grind. The emphasis on this grind is strength, as the edge is often left thick, and thickens dramatically and quickly past the edge. Cutting ability is sacrificed to some extent for durability. This is a format you'll often see on knives that will take prying, digging, and chopping abuse, such as the "sharpened prybar" type knives. This grind does show up for other uses as well, such as utility use.

Chisel
The chisel grind is ground on one side only. One side of the blade has an edge bevel on it; the other side is completely flat. Because of this, the edge on a chisel-ground knife is usually extremely thin and sharp and cuts very well. On the downside, the asymmetrical grind causes the knife to veer off course during cutting chores; it also thickens dramatically. This format has become popular on tactical knives, often coupled with a clip-point Americanized-tanto blade.
Scandinavian Single-Bevel
Scandinavian knives, such as the puukko, often sport a grind that looks like a saber grind. However, there are no secondary edge bevels, which leaves the edge extremely thin and incredibly sharp. Due to the sharpness of the edge, these knives will often outcut just about anything.

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