About FX Legal Carry Knives
A folding knife concept for regions with strict knife laws
FX Legal Carry Knives is a concept created for one reason: to offer a folding knife that looks and feels full-size, while being designed to comply with strict blade-length limits and non-locking requirements in many jurisdictions.
I did not start FX to “beat” conventional folding knives. I started it because I kept encountering the same situation time and again: a person wants a practical, full-hand folder for everyday life—but local knife laws make that kind of knife difficult or impossible to carry legally.
Knife laws and enforcement practices vary by country and region and may change over time. Buyers are responsible for checking local regulations and ensuring lawful carry and use.
Who I am
My name is Denis Cherevichnik. I am a weapons historian, arms researcher, and knife maker working between Riga (Latvia) and Sheffield (England).
For almost 25 years, my professional work has been connected with knives—their history, construction, legal regulation, and use. I am the author of multiple peer-reviewed academic papers and two monographs devoted to edged weapons. For more than fifteen years, I have been making handmade folding knives, and I hold several European patents related to folding-knife construction.
Here you can find examples of my work beyond this project, including more complex and historically inspired pieces:
II also maintain a long-standing researcher profile on Academia.edu, which is ranked in the Top-5 in its field as a weapons historian profile.
FX is not a “brand story” invented by a marketing department. It is the result of years of research, workshop practice, and real prototypes on the bench—tuning geometry, tolerances, spring strength, and safety details until the concept became reliable and repeatable.
I learned the craft in regions where traditional knife-making schools still exist—primarily in France (Thiers) and Spain (Albacete). These traditions, together with historical sources from the eighteenth and nineteenth centuries, continue to shape my design choices, mechanics, and construction philosophy.
For over ten years, I have been running my own five-star Etsy shop selling my knives.
Why FX Knives exists
Another major field of my research is the history of knife legislation—from the laws of the Roman Empire to modern criminal codes. In my academic work, I analyze not only how these laws were written, but also how they were applied and interpreted in practice, historically and today. This perspective allows me to view knife legislation in the long term, tracing continuities and changes across centuries.
Over the past decade, many European countries—followed by others worldwide—have significantly tightened knife laws. Blade-length limits, restrictions on locking mechanisms, and limitations on one-handed opening have become increasingly common.
When this trend accelerated, I decided to approach the problem not as a loophole hunter, but as a weapons historian, a trained lawyer, and a designer. I wanted to create a folding knife that:
• complies with strict blade-length limits under conservative measurement
• does not rely on legal ambiguity or interpretive tricks
• remains safe, reliable, and practical
• looks and feels like a full-size knife in hand, not a compromised object
The FX Legal Carry Knives concept
The FX Legal Carry Knives concept was created to solve one specific, modern problem.
In many parts of the world—entire countries, individual states, or even particular cities—carrying a full-size folding knife is no longer lawful. Blade-length limits are tightening; bans on locking mechanisms and one-handed opening are being introduced; and restrictions on tip shape and blade geometry are becoming more common. At the same time, enforcement practice may differ from the literal wording of the law, and the outcome of an encounter often depends on practical interpretation rather than statute alone.
Most attempts to create a “legal” folding knife follow one of two paths.
The first is to scale the entire knife down to meet the required blade length. Under limits of 2.5–3 inches (as in Japan and a number of European jurisdictions), this often results in a miniature knife with a short handle—uncomfortable, potentially unsafe to hold, and poorly suited to everyday practical tasks.
The second path is to keep the knife full-size but reduce the length of the cutting edge by leaving an extended ricasso. In this approach, a blade of roughly 4–4.5 inches may have only about 3 inches sharpened, while the rest remains unsharpened in the hope that only the cutting edge will be measured during inspection.
These approaches may be lawful in certain jurisdictions and under specific interpretations, but they inherently rely on legal ambiguity rather than on a single, conservative measurement standard.
Both approaches rely either on compromised ergonomics or on legal uncertainty and the risk of arbitrary interpretation.
As a result, such designs build legal uncertainty into the knife from the outset: every encounter with police or regulatory authorities becomes a lottery shaped by local practice, internal guidelines, and subjective judgment. Even when it is sometimes possible to persuade authorities to measure only the cutting edge, this does not create a stable legal basis. It merely confirms the absence of a single, repeatable criterion.
For that reason, as a weapons historian and a lawyer by training, I deliberately refused that dead-end approach.
At the core of the FX concept is maximum legal clarity.
The blade length of every FX knife is designed to remain within strict limits when measured using a conservative, widely accepted method—from the tip to the front edge of the handle liners. No extended ricassos used as an argument. No alternative measurement methods. No grey areas.
At the same time, I did not want to create a knife that looked or felt like a compromise. Instead of manipulating the blade, I rethought the handle construction.
The visual and ergonomic impression of a full-size folding knife is achieved not by extending the blade, but by extending the handle liners. These rigid structural elements protrude beyond the bolster line and visually continue the blade. Their width, material, and finish are not merely coordinated with the blade—they replicate it completely. The liners share the same width, planar geometry, and hand-finished satin surface as the blade.
Because of this, the boundary between blade and protruding liners is scarcely perceived as a break in form. If the thin transition line is obscured, it becomes visually impossible to distinguish the liners from the blade itself—they read as a single continuous element.
The result is a purely optical effect—deliberate, honest, and technically justified.
The blade, unless examined closely, appears full-size, while its actual length remains strictly within the most demanding legal limits. For this effect to function not only in photographs but in real use, the liners could not be decorative. Thin protruding elements without sufficient stiffness would inevitably deform.
For this reason, FX knives use liners made from hardened stainless steel or Grade 5 titanium—materials chosen specifically for strength, dimensional stability, and long-term durability. Technically and legally, what is extended is the handle—its fixed structural component—not the blade.
The unsharpened portion of the blade is fully hidden inside the handle and does not factor into blade-length calculations. It exists solely for structural and safety reasons.
This combination of legal transparency, structural honesty, and visual coherence defines the FX concept.
FX knives are not intended to outperform ordinary full-size folding knives in countries and regions where such knives are legal. In those places, a conventional folder with a 100–110 mm blade is often simpler and more convenient. FX Knives are made for special conditions.
These knives were designed for jurisdictions with the strictest regulation of folding knives—places where ordinary full-size folders cannot be carried legally.
However, their relevance is not limited to those jurisdictions alone. FX Knives also suit people living under vague or unclear laws, where the maximum permitted blade length is ambiguously defined and enforcement practice can vary widely.
Global trends indicate that legislation governing the carry and sale of EDC knives is gradually tightening. The FX concept helps knife users remain on the right side of the law without abandoning the familiar feel of a full-size knife. These knives look and handle like full-size folders, while being designed to comply with blade-length and construction limits—without disputes, grey zones, or uncertainty.
Safety and the FX Knives mechanism
FX Knives are built around the French cran force spring—an improved slipjoint developed in the 1820s by Jean-Pierre Calmels, associated with the Laguiole tradition.
From both a legal and technical standpoint, cran force is a non-locking mechanism. Mechanically, it combines the best features of slipjoints and lockbacks:
• no constant spring pressure during closing
• no “guillotine” effect
• no blade play developing over time
• two-handed operation by design
In addition, FX Knives incorporate a structural safety feature: even in the unlikely event of an unexpected closure, the cutting edge is designed not to contact the user’s fingers. Any contact would occur only with the ricasso—the unsharpened portion of the blade—fully enclosed inside the handle when the knife is open.
This choice was driven by the fact that, in many jurisdictions with strict EDC regulations, locking folders and sometimes one-handed opening are prohibited. In some regions, both are restricted. FX Knives equipped with the cran force slipjoint meet these requirements while remaining mechanically secure. Because of the strength of the spring, opening the knife is realistically possible only with two hands.
For regions with less restrictive laws—where blade length is limited but locking and one-handed opening are permitted—I am preparing a line of FX Legal Carry Knives with a lock-back mechanism.
Blade shape and legal considerations
Knife laws, and the way they are enforced in practice, may vary not only by blade length but also by blade shape.
In some jurisdictions, enforcement practice may treat certain pointed profiles as problematic. For this reason, FX Knives can be configured with pointed tips for more liberal environments, as well as with non-pointed or rounded profiles where pointed blades are legally sensitive.
Alternative shapes include wharncliffe, sheepfoot, lambfoot, and talon. This approach allows the knife to be adapted not only to legal requirements, but also to cultural expectations and real-world enforcement practices in different countries.
What FX Knives are—and what they are not
To avoid misunderstanding, it should be stated clearly: FX Knives do not outperform ordinary full-size folding knives in functionality, capability, or convenience.
In countries without strict restrictions on blade size, a conventional EDC folding knife with a 100–110 mm blade is often more practical and comfortable. In such places, FX Knives offer no real advantage.
The strengths of the FX Knives concept become evident only where strict limits apply to blade length and to the mechanism type or opening method. In those jurisdictions, FX Knives provide a lawful alternative to full-size folders—without relying on legal loopholes or questionable interpretations.
The FX concept is not about being technically superior.
The FX concept is about being able to carry a knife legally under strict constraints.
A simple solution to a complex problem
I do not consider the FX concept revolutionary or a technological breakthrough. It is a relatively simple—though original—technical solution to a legal problem: one of many possible approaches.
It is not “rocket science.” But it is an honest, transparent solution designed for real use, not merely for meeting paper requirements. Innovation does not have to be complex; it has to make everyday life easier and more practical.
If you live in a place where carrying a full-size folding knife is legally difficult, FX Legal Carry Knives were created for you.
Legal protection of the FX Knives concept
My interest in intellectual property law dates back to my time at law school in the 1980s. Beginning in the mid-1990s, I have been actively registering trademarks, brands, and design rights in multiple jurisdictions. By the time I began work on the FX Knives concept, my portfolio already included roughly two dozen registered trademarks, brands, and protected designs in different countries, including several European registrations related to folding-knife construction.
After extensive prototyping, testing, and refinement—and once a series of finalized prototypes had been completed—I decided to secure formal legal protection for the FX construction in the form of a Registered Design.
In 2024, the FX Knives concept was officially granted Registered Design protection, covering the core structural and visual characteristics of the FX construction. The rationale was straightforward: if relatively simple design features in folding knives are eligible for formal legal protection, then a structurally novel and more technically refined solution fully justifies registration as an official Registered Design.