The History of the Back Lock Folding Knife

Modern lock-blade folding knives encompass a wide variety of lock mechanisms. Although many of them are relatively recent innovations, others trace their origins back hundreds of years to the earliest days of their genre. The grandfather of them all, however, is the back lock. To truly appreciate this brilliantly simple design, it helps to understand the rich history of its evolution.

The oldest known folding knife is believed to be about 2,500 years old. Known as the “Hallstatt Knife,” it was discovered near Hallstatt, Austria, and is estimated to date back to between 600 and 500 BCE. Made of iron and bone, it featured a hawkbill-style blade, a metal bolster, and simple “friction folder” style of construction. Amazingly, the folding knife’s basic form would remain largely unchanged for almost 2,000 years before the advent of lock-blade folding knives.

Through the late Middle Ages, all classes of society in Europe were generally allowed to carry swords. By the mid-18th century, however, a variety of laws were passed that limited sword carry exclusively to members of the nobility. Additional laws restricted the production of weapons themselves, forcing craftsmen to adapt their skills to the creation of other products. This paradigm shift, along with the concurrent development of spring steel, inspired the development of a new category of knife—large, lock-blade folding knives like the Spanish navaja.

Navaja is derived from the Latin word novacula, meaning razor. This style of knife originated in the Andalusian region of southern Spain in the late 1600’s. While earlier “peasant knife” versions of the pattern were friction folders, the advent of spring steel paved the way for their evolution into lock-blade knives. Craftsmen discovered that they could add a steel backspring to the outside of the knife’s handle, anchoring it at the butt end so the front end could flex and apply pressure to the tang of the blade. When the blade was opened, a shoulder in the back of the blade contacted the front edge of the spring, stopping its opening arc. Simultaneously, a hole drilled in the forward section of the backspring engaged a notch in the top of the blade tang. Together, these contact surfaces applied pressure in opposite directions and provided two of the three points needed for the triangular geometry of a folding knife lock mechanism. The blade’s pivot pin provided the third.

The earliest navaja patterns featured a single locking notch and had to be unlocked by manually lifting the front of the spring, which typically had flared and sometimes ornate “ears” to provide a purchase. Later, craftsmen attached a ring or lever to the spring to make releasing the lock easier. They also added a series of locking notches that produced a distinctive ratcheting sound as the blade was opened. Like racking the action on a modern pump shotgun, this noise was sometimes used to warn or intimidate a potential adversary and led to the navaja’s onomatopoeic nickname, the carraca.

After the development of the Spanish navaja, cutlers in Italy and France followed parallel paths. They created their own signature styles of folding knives with blade locks based on fixed back springs.

French lock-blade knives, called “palm knives,” used a wide, external backspring that resembled a palm leaf and a single tang notch. The forward section of the backspring was bent upward and fitted with a metal ring to facilitate lifting the backspring to release the lock.

Rather than an external spring, Italian knifemakers used a narrow backspring the same thickness as the blade along most of its length. Instead of a tang notch, they filed an integral pin into the spine of the blade. This pin could be round or square, but served the same mechanical purpose as the notch. When the blade was opened, the front edge of the backspring stopped its rotation. At that point, a matching hole in the forward portion of the backspring aligned with the tang pin and snapped down over it to lock the blade. To release the lock and close the blade, the front of the backspring had to be manually lifted to clear the tang pin. Later known as a “picklock” mechanism, this style of lock often featured ornamental “ears” on the forward portion of the backspring to allow a firm grip when releasing the lock. Italian knifemakers later added rings and levers to make the lock release easier; however, the “picklock” style of manually released lock was widely used on Italian switchblades until the mid-20th century.

As the back lock concept continued to evolve, its mechanism became more streamlined. The backspring was still anchored at the rear of the handle, but it was the same thickness as the blade along its entire length. The flared “ears” at the forward end were replaced with a simple squared “lug” that extended from its lower surface to fit into a matching notch in the rear portion of the blade tang. When the blade was opened, the front surface of the backspring would stop its opening arc. The spring tension of the backspring would drive the lug down into the tang notch, where the front and back surfaces of the lug, in concert with the pivot pin, created the three-point triangular geometry necessary to lock the blade securely.

This style of lock was slimmer than the locks with the flared “ears,” but required a ring or lever to facilitate lock release. It also offered a smoother, safer action than previous designs and a better “self-close” function. In the closed position, the tension of the backspring caused the bottom surface of the lug to contact the bottom of the blade tang. This flat-to-flat contact served as a detent to ensure the blade would stay reliably closed when not in use. Many earlier designs relied on friction or, in switchblades, the retention of the firing button, to keep the blade closed.

The addition of rings and levers made the operation of early back-lock-style knives easier; however, these features were somewhat cumbersome and required two hands to close the knife. 

To simplify both the operation and the construction of these knives, the next innovation was to create a pivoting lock bar driven by a separate leaf spring. This mechanism used the same “lug-and-notch” lock interface, but the lug was part of a separate lock bar that pivoted at the center like a seesaw. The rear end of the lock bar was supported by a flat or round leaf spring that was anchored to a backspacer in the butt end of the handle. The spring’s upward pressure on the rear of the lock bar created a constant downward pressure on the front, lug end. With the blade folded, this pressure created a strong “self-close” to keep the blade authoritatively closed. When the knife was opened, the same pressure would drive the lug into the tang notch to lock it. However, to close the knife, the user simply pushed down on the rear of the lock bar to raise the front end. This made operation of the lock release much more convenient and defined the basic form of the back lock mechanism still in use today. It also inspired one of the alternate names for this mechanism, the “rocker lock.”

By the mid 19 ^th century, the back lock was widely used by knifemakers throughout Europe. The lengths of the lock bar varied from roughly half the handle’s length to its full length, as did the style of the release. In “humpback” knives, the rear portion of the lock bar stood proud above the handle for easy access. Others set the standard for the modern style in which the lock bar is flush with the profile of the handle and a scalloped recess in the handle allows the lock release to be depressed.

In 1964, Buck Knives® introduced the Buck Model 110 Folding Hunter®, which would become one of the most iconic knives ever created. It and its smaller companion, the model 112 Ranger®, set the standard for folding knife form in the 1960’s and 1970’s. Many other companies—including Puma, Schrade, Camillus, and Old Timer, to name a few, emulated these designs and their full-length back lock mechanisms. Although the longer lock bar provided enhanced lock strength and leverage, it made one-handed closing of the knife more challenging.

In the late 1960’s, aspiring custom knifemakers Harvey McBurnette, Dick Dorough, and W.T. Fuller worked together at a tire factory in Alabama. After Fuller tragically lost one of his hands in an industrial accident, the three men joined forces to design a folding knife for Fuller that could be easily operated with only one hand. They took the full-length back lock that dominated the market at the time, shortened the lock bar, and adjusted the spring tension to ensure reliable lock engagement. This “front lock” or “mid back lock” folder allowed the lock to be easily released using only one hand and established a trend for modern back lock folding knives. Although this design certainly had historical precedent in traditional “humpback” folders, it was distinctly different from the other knives marketed at the time.

Al Mar was a former U.S. Army Special Forces soldier with a Master’s Degree in Industrial Design. During the 1970’s, he worked for Gerber Legendary Blades and was responsible for some of their most successful designs of that era. In 1977, he left Gerber to found his own company, Al Mar® Knives. Heavily inspired by the custom makers of the time—including Harvey McBurnette—Mar appreciated the advantages of the front lock design that McBurnette favored and decided to incorporate it into his tactically oriented line of folding knives. Early Al Mar knives showcased this lock design, with full credit given to McBurnette for the inspiration.

A few years after establishing his own company, Mar introduced Spyderco co-founder Sal Glesser to his production partners in Japan. That introduction was not only instrumental to establishing Spyderco as a knife manufacturer, but also helped define the form of our earliest designs. With it, Mar gave his blessing for Sal to incorporate the mid-back lock into Spyderco folders.

In 1981, Sal Glesser’s Worker™ design revolutionized the form of the modern folding knife. Its pocket clip offered convenient, top-of-the-pocket carry, while its Trademark Round Hole™ allowed swift, positive, one-handed opening with either hand. Combined with the ease of one-handed closing afforded by the mid back lock mechanism, these features set a new standard in the efficiency, speed, and reliability of folding knife operation. Aesthetically, the Worker’s uniquely different look also ushered in a new era of folding knife design.

Today, the back lock still offers many significant performance advantages, including strength, reliability, ease of use, completely ambidextrous operation, a strong self-close function, and a reassuring audible “click” each time the lock engages. These qualities are further enhanced by state-of-the-art manufacturing methods that ensure exacting tolerances and the precise fitment of mating parts. Although it has evolved to incorporate subtle refinements like the Boye Dent—a scallop in the rear of the lock bar to help prevent unintentional lock release—its basic form has remained substantially unchanged. The product of a long and fascinating evolutionary process, the back lock is rightfully here to stay.