A clarion call of so many in today’s information age is, “Why can’t life be simpler?” It often seems as though we’re deluged with data from every angle and on every subject. And, yes, some of this so-called knowledge really is extraneous. But each discipline, no matter how small, has its own technicalities, complications, and terms. If you want to understand, say, stocks or ranching or figure drawing or playing the ukulele, then you’ll need to know some basic vocabulary before you dive right in — and the same is true when it comes to OTFs.

In this article, we’ll define and briefly discuss some of the most important knife-related terms and ideas you should know about knives in general and OTF knives in particular.

The Parts and Functions of an OTF

Out-the-front (OTF) knives share almost all of the basic characteristics of other kinds of knives. They have a handle and a blade, concepts so common that they hardly need defining. However, some of the smaller elements of both blade and handle will have immense importance for how a particular OTF presents and performs, elements such as the blade’s …

• Edge: the sharpened part of the blade. All edges are not created equal, and as we will see in the “Common Types of Blade Shapes” section below, a specific edge can determine the shape, length, and usage of a knife.
• Spine: the blunt back of a blade. The spine easily accepts a stabilizing thumb or finger, making it easier to do delicate work. Note that double-sided knives don’t have spines, which substantially changes their performance.
• Point: the piercing tip of a blade. Like edges, points initially seem simple, but vary substantially from knife to knife. Blade shapes may minimize or maximize the point depending on their intended purposes.

We’re only three definitions in, and already you can see that the seemingly “simple” parts of a knife have hidden complexities. That’s doubly true when we consider the distinguishing characteristics of OTFs and the wider family of knives to which they belong, namely …

• Automatic Knives: a broad category of folding or sliding knives that distinguishes itself by instantly deploying. Sometimes, people use the word “switchblade” as a synonym for automatic knife, but that’s a misnomer.
• Out-the-Side (OTS) Knife: a type of automatic knife with a pivot point similar to folding knives and a blade that deploys in a 180° arc. Switchblades are prototypical OTS knives.
• Out-the-Front (OTF) Knife: a type of automatic knife that thrusts directly out of the handle when deployed. While in the same general grouping as OTS knives, OTFs work and feel dramatically different.
• Gravity Knives: a type of automatic, OTF knife that uses gravity rather than stored kinetic force (i.e., a spring) to deploy. Originally designed in the early 20th century for German paratroopers, the gravity knife typically features only a securing latch. By pointing the knife downward and releasing the latch, a user allow the blade to drop out of the handle and into locking position. For somewhat unclear reasons, gravity knives are often illegal to carry in areas where other kinds of automatic knives may be legal.
• Ballistic Knives: a type of automatic knife that fires its blade like an arrow. Ballistic knives can be powered by springs, gas, or compressed air. Federally illegal in the United States.

OTFs and their relatives also vary according to their locking and trigger mechanisms, which are …

• Tang Lock: a knife that locks onto the small part of the blade that remains in the handle after deployment. Tends to be less stable on an OTF.
• Frame Lock: a knife that locks farther down into the frame of the blade. Tends to be more stable on an OTF.
• Spine-Mounted Lever: a sliding deployment mechanism located on the spine of an OTF’s handle.
• Body-Mounted Lever: a sliding deployment mechanism located on the body of an OTF’s handle.
• Plunge Lock / Button Lock: a deployment mechanism located on the body that engages when pressed.

As you can see, even the basic elements of OTFs require some specialized knowledge to properly understand. That’s even more true when talking about the materials used in their creation.

Characteristics of Steel

The most important and most talked about material used in OTFs, and not only does it majorly impact the way you use a knife, it also features prominently in many marketing materials. How can you sort fact from hype and make wise buying decisions or determine which tasks are best suited for specific blades? Part of that involves knowing a number of steel-related terms.

To start with, the first thing you should know is the vocabulary related to steel. Steel has multiple characteristics defined by several technical terms, such as …

• Hardness: a metal’s ability to resist permanent deformation when force is applied. Hardness is one of the most important characteristics of knife steel and so important that the following section is entirely devoted to it.
• Toughness: a metal’s ability to resist breaking when force is applied. While it sounds similar to hardness, toughness measures an entirely different characteristic. In fact, hardness and toughness are often inversely related with extremely hard materials having reduced toughness. (Think of hard substances such as glass are also very easy to shatter.)
• Ductility: a metal’s ability to stretch and deform when put under tension. Ductility is a related concept to hardness and toughness, one that specifically measures how easily a metal can be drawn into a wire. You will not usually encounter detailed ductility descriptions as a knife-purchasing consumer, but it’s very important for knife manufacturers.
• Ability to Retain an Edge: a metal’s ability to cut for an extended period after sharpening. A metal’s edge retention is generally positively related to hardness, but it can prove difficult for extremely hard or tough steels to be sharpened to the proverbial razor’s edge.
• Corrosion Resistance: a metal’s ability to avoid rusting when exposed to moisture. Corrosion resistance greatly influences how you will use a specific kind of knife, and it is often somewhat negatively correlated with hardness.

While it’s beneficial to know all of these terms, you will most commonly encounter references to hardness, corrosion resistance, and edge retention when looking to buy an OTF. Out of those three, hardness is by far one of the most important elements of knife steel.

Terms Related to Steel Hardness

Indeed, knife steel is so vital to making an informed buying decision about specific knives that it’s worth learning a little about the means of its measurement. There are two basic ways in which experts measure steel: the Mohs scale and the Rockwell scale.

The Mohs scale is by far the simpler of the two measurements. Developed in the early 19th century by one Friedrich Mohs, it functioned by arbitrarily assigning numbers in ascending value of hardness to various minerals such as talc (1), fluorite (4), quartz (7), and diamond (10). When evaluating an unranked material, testers would attempt to scratch it with the 10 charted minerals to determine its hardness. While the Mohs scale does record the hardness of various metals, it is more often used by jewelers and geologists than by knifemakers.

The hardness scale preferred by those working with steel and similar metals is the Rockwell scale. A pair of men named Hugh Rockwell and Stanley Rockwell (no relation) created a machine that applied various predetermined loads to a metal. The machine would then determine if the load had managed to leave an indentation after striking. The Rockwell scale offers far more rigorous and detailed evaluation of materials than the Mohs scale, but it is also far more complicated. A Rockwell scale result will include a scale letter, an abbreviation, and a hardness number.

All of the steels used by knifemakers are part of the Rockwell C scale, and its abbreviation is HRC. It’s not uncommon for vendors to dispense with both labels and simply list the hardness number by itself. On one extreme, soft steels will rate in the low fifties, while very hard steels will rate in the mid-sixties.

Types of Steel Used in OTFs

Once you know a bit about the characteristics and technical measurements of steel, it helps to acquaint yourself with the specific kinds of steel commonly found in knives. A few of those include …

• 420: the standard, inexpensive steel grade. It’s tough, hard, and reasonably non-corrosive, but it dulls quickly.
• 14C28N: a Swedish budget steel that features improved edge retention over 420 steel.
• 440C: an upgraded version of 420 steel that’s slightly less tough, but that keeps an edge for longer. Common in everyday carry (EDC) knives.
• D2: a corrosion-resistant, non-stainless steel originally designed for tools. Extremely well-rounded and with a mid-range price point.
• 154CM: an easy to sharpen and rust-resistant steel that’s preferred by many knife makers. A mid-market steel, it was originally intended for use in industrial contexts.
• M390: a high-end steel that’s sintered (i.e., formed through the simultaneous heating and pressing of powdered material) during its creation. It’s very difficult to sharpen, but balances that with impressive hardness, toughness, and corrosion resistance.
• MagnaCut: a bespoke steel intentionally created for use in knives. Very tough, hard, and easy to sharpen with an incredible resistance to corrosion. Super-premium and difficult to come by.

Typical Handle Materials

Fortunately, handle materials (which are every bit as important as steel when it comes to creating a knife) are generally less complex. True, they’re even more numerous than steel types, but they break down into three main categories:

• Natural Materials: organic substances naturally found in the environment. This category is far and away the most diverse out of the three and includes things such as wood, bone, nacre (i.e., mother of pearl), rawhide, stone, leather, and horn. This is the oldest category of knife handle materials and also particularly challenging since most natural materials are vulnerable to moisture and impacts.
• Metals: In contemporary knifemaking, the handle of a knife is almost as likely to be made of metal as the blade. Well, perhaps that’s something of an exaggeration, but metallic handles are quite common. Typical options include aluminum, titanium, and stainless steel.
• Synthetics: manmade materials created in artificial environment. Synthetic knife handles vary wildly in durability, usefulness, and price. Some common examples include Micarta (a tough and highly customizable resin composite), G-10 (a laminated fiberglass composite), Kraton (a thermoplastic rubber susceptible to water infiltration), carbon fiber (a strong, light, and brittle composite that suspends woven carbon filaments in resin), and Zytel (a robust, tough, abrasion-resistant thermoplatic that’s cheap to produce and has a notoriously cheap feel).

Common Types of Blade Shapes

Our final section deals with yet another variable, namely the distinctive shapes of knife blades. Far from being a merely decorative flourish, blade shapes largely determine which tasks are appropriate for a particular knife. Some standard blade shapes are …

• Drop Point: a shape where the spine of the knife gradually drops to meet the upward sweep of the cutting edge. An incredibly common design. When you imagine a folding knife, this is probably the shape you envision.
• Clip Point: a shape where the spine continues straight until the midway point and then drops in an abrupt swoop to meet the point. This is the shape of the iconic Bowie knife.
• Trailing Point: a double-sided design where both the spine and the edge turn upward toward the point, the latter far more dramatically. Most of the spine in a trailing point will be sharpened, making such knives primarily suitable for filet work.
• Spear Point: a bilaterally symmetrical, double-sided design that looks, as you might’ve guessed, just like a spear’s point. The dagger style is very closely related to the spear point shape.
• Tanto: a shape inspired by the Heian-era Japanese sword design of the same name (短刀). This style of knife features an exaggerated, chisel-shaped blade. The reverse tanto is an inverted reflection of the design with a spine that abruptly angles down to a piercing point.
• Straight Back: a shape with an entirely straight spine. Also called a standard blade shape.
• Wharncliffe: a thick blade shape with a straight cutting edge and a spine that gently slopes toward it. This design minimizes the blade’s point, making it appropriate for EDC situations rather than self-defense situations. The sheepsfoot blade is a related shape with an even more dramatically curving spine and smaller piercing point.
• Hawkbill: a shape with a radically curved spine that leaves this blade with a hooked tip. Somewhat reminiscent of a scythe. The karambit bears some resemblance to the hawkbill, although it is intended to be used for self-defense instead of utilitarian tasks.

While there are a slew of terms you should acquaint yourself with if you want to become familiar with the world of OTFs, understand that this list is only the beginning! Check out our blog for more information or browse our full selection of knives.