A folding knife connects the blade to the handle through a pivot, allowing the blade to fold into the handle. To prevent injury to the knife user through the blade accidentally closing on the user’s hand, folding knives typically have a locking mechanism. Different locking mechanisms are favored by various individuals for reasons such as perceived strength (lock safety), legality, and ease of use. Popular locking mechanisms include:
Lockback – Also known as the spine lock, the lockback includes a pivoted latch affixed to a spring, and can be disengaged only by pressing the latch down to release the blade.
Liner Lock – Invented by Michael Walker, uses a leaf spring-type liner within the groove of the handle that snaps into position under the blade when it is deployed. The lock is released by pushing the liner to the side, to allow the blade to return to its groove set into the handle.
Button Lock – Found mainly on automatic knives, this type of lock uses a small push-button to open and release the knife.
Frame Lock– Also known as the integral lock or monolock, this locking mechanism was invented by custom knifemaker Chris Reeve for the Sebenza as an update to the liner lock. The frame lock works in a manner similar to the liner lock but uses a partial cutout of the actual knife handle, rather than a separate liner inside the handle to hold the blade in place.
Another prominent feature on many folding knives is the opening mechanism. Traditional pocket knives and Swiss Army Knives commonly employ the nail nick, while modern folding knives more often use a stud, hole, disk, or flipper located on the blade, all which have the benefit of allowing the user to open the knife with one hand. The wave feature is another prominent design, which uses a part of the blade that protrudes outward to catch on one’s pocket as it is drawn, thus opening the blade.
Automatic or switchblade knives open using the stored energy from a spring that is released when the user presses a button or lever or other actuator built into the handle of the knife. Automatic knives are severely restricted by law in most American states.
Increasingly common are assisted opening knives which use springs to propel the blade once the user has moved it past a certain angle. These differ from automatic or switchblade knives in that the blade is not released by means of a button or catch on the handle; rather, the blade itself is the actuator. Most assisted openers use flippers as their opening mechanism. Assisted opening knives can be as fast or faster than automatic knives to deploy.