Types

Form

Fixed Blade Knives
A fixed blade is a knife in which the blade does not fold and extends most of the way into the handle. This type of knife is typically stronger and larger than a folding knife. Activities that require a strong blade, such as hunting or fighting, typically rely on a fixed blade. Some famous fixed blade designs include the Ka-bar and Bowie knives.

Folding Knives
A folding knife is one that has a pivot between handle and blade, allowing the blade to fold into the handle. Most folding knives are small working blades, pocket knives are usually folding knives.

Some folding knives have a locking mechanism:

• The most tranditional and commonplace lock is the slip-joint. This isn't really a lock at all, and is found most commonly on traditional pocket knives. It consists of a backspring that wedges itself into a notch on the tang on the back of the blade.
• The lockback is the simplest true locking knife. It is found on most traditional locking knives. It is like a slip-joint, but the lock consists of a latch rather than a backspring. To disengage, one presses the latch on the spine of the knife down, releasing the tang.
• The linerlock is the most common today on knives, especially so-called "tactical" folders. Its main advantage is that it allows one to disengage the lock with one hand. It consists of a liner bent so that when the blade opens, the liner presses against the rear of the tang, preventing it from swinging back. To disengage, you press the liner to the side of the knife from where it is attached to the inside of the scales.
• The framelock is a variant of the linerlock, however, instead of using the liner, the frame functions as an actual spring. It is usually much more secure than a liner lock.
• There are many other modern locks with various degrees of effectiveness. Most of these are particular to single brands, most notably Benchmade's AXIS(tm) lock and SpyderCo's Compression(tm) lock.

Function

In general, knives are either working, or fighting knives.

• A bread knife is a special knife with a longer, serrated blade especially designed for easily cutting all types of bread. The blade is straight with a blunt end. The serrations (teeth) allow it to cut bread using less vertical force, so keeping the bread from being compressed. They also leave less crumbs than most other knives.
• A hunting knife is normally used to dress large game. It is often a normal, mild curve or a curved and clipped blade.
• A stockman's knife is a very versatile folding knife with three blades: a clip, a spey and a normal. It is one of the most popular folding knives ever made.
• A dive or diver's knife is adapted for underwater use. Dacor (http://www.divedacor.com) dive knives have tough thermal plastic handles, durable sheaths, and a convenient push-button release, for example.
• Utility, or multi-tool knives may contain several blades, as well as other tools such as pliers. Examples include Leatherman, SOG, Gerber and Victorinox (The "Swiss Army knife") tools.
• An electrician's knife is specially insulated to decrease the chance of shock.
• A kukri is a Nepalese fighting and utility knife with a deep forward curve.
• A machete is a long wide blade, used to chop through brush. This tool (larger than most knives, smaller than a sword) depends more on weight than a razor edge for its cutting power.
• A survival knife is a sturdy knife, sometimes with a hollow handle filled with equipment. In the best hollow-handled knives, both blade and handle are cut from a single piece of steel. The end usually has an O-ring seal to keep water out of the handle. Often a small compass is set in the inside, protected part of the pommel/cap. The pommel may be adapted to pounding or chipping. Recommended equipment for the handle: a compass (usually in the pommel). Monofilament line (for snares, fishing), 12 feet of black nylon thread and two needles, a couple of plastic ties, two barbed and one unbarbed fishhook (unbarbed doubles as a suture needle), butterfly bandages, halizone tablets, waterproof matches.
• Special purpose blades may not be made of metal. Plastic, wood and ceramic knives exist. In most applications, these relatively fragile knives are used to avoid easy detection. Custom-made knives with diamond edges are used to make ultrathin slices of samples for use with an electron microscope.