Different Mechanisms, Different Hazards
Folding, switchblade, and specialty knives must not be confused with retractable knives. A retractable blade is supposed to collapse into the handle when its point meets resistance. The blades discussed here move from a concealed or folded position into an exposed position, where they are intended to remain.
Any working mechanism introduces hazards not present in a fixed-blade prop. A blade may close unexpectedly, open before it is wanted, catch on clothing, pinch the hand, or fail to lock securely into position. A blunt or lightweight blade may reduce some dangers, but it does not eliminate those created by the mechanism itself.
Such a mechanism should be used only when its operation provides a necessary theatrical effect. If the audience does not need to see the blade open, unfold, or otherwise appear, use a simpler and more dependable prop.
Folding Knives
An ordinary folding knife has a blade that pivots into the handle. Some designs lock the blade in the open position; others rely only on friction or spring pressure to hold it there.
A non-locking blade must never be used for contact choreography. Pressure against the back of the blade can fold it into the actor’s fingers. Even a locking knife must be inspected and tested to ensure that the lock engages fully and cannot be released accidentally during handling.
Opening and closing the knife present hazards of their own. Fingers may be pinched between the handle and blade, and a careless grip may place them directly in the blade’s path. These actions must be treated as part of the choreography rather than as casual business added by the actor.
If a folding knife will be used during physical contact, its blade must remain securely fixed in the open position. When the act of opening the knife is important as a theatrical moment, the safest solution may be to perform that action with the working prop and substitute a fixed-blade version before the fight begins.
A thumb stud attached to the blade permits some folding knives to be opened with one hand. Certain models use an internal spring or torsion bar to assist the movement after the actor begins pushing the blade open. These are assisted-opening folding knives, not switchblades: the thumb moves the blade itself rather than releasing a spring-powered blade from the handle.
Switchblade and Gravity Knives
A switchblade knife—technically an automatic knife—uses a spring-powered mechanism to open the blade when a button or lever in the handle is pressed. A gravity knife releases its blade so that gravity carries it into position, sometimes assisted by a movement of the hand.
In a side-opening switchblade, the blade swings from the side of the handle. The spring opens it, but does not return it. The lock must be released and the blade folded back into the handle manually—normally, and most safely for theatrical use, with two hands.
A gravity knife does not depend upon a spring to propel the blade. Releasing a catch allows gravity, inertia, or a combination of the two to carry the blade into position. If the opening points downward, the blade may simply drop into place. Otherwise, a flick of the wrist supplies the necessary movement and can deploy the blade regardless of which way the opening is facing.
An out-the-front knife, or OTF, is one whose blade travels through the end of the handle. The term describes the direction of movement only. An OTF knife may be operated by gravity or by a spring-powered mechanism, and a spring-powered model may be either single-action or double-action. In a single-action design, the mechanism drives the blade outward but it must be returned manually. In a double-action design, the same control both extends and retracts it.
Some military out-the-front gravity knives are sometimes referred to as paratrooper knives because of their historical association with airborne troops. The term does not apply to all OTF knives.
All of these mechanisms create opportunities for unintended deployment, incomplete opening, or failure to lock. A blunt blade does not prevent the handle or moving blade from pinching, striking, or cutting the performer. Nor does it make an unreliable mechanism acceptable.
A spring-loaded knife is often accompanied by a sharp flick of the wrist. The gesture contributes nothing to the opening; the spring has already done the work. It is a cinematic flourish used to make the action appear more menacing—the knife equivalent of working the action of a semi-automatic firearm that is already ready to fire. If such a flourish is wanted for theatrical effect, it must be separately justified and rehearsed.
Butterfly Knives
A butterfly knife, or balisong, has two handle sections that rotate around the blade. When folded, the handles enclose it. To open the knife, the handles are swung apart and brought together on the opposite side.
Butterfly knives have a much longer history, but their visibility in American popular culture rose sharply beginning in the late 1970s. Their rapid, conspicuous opening made them particularly attractive for film and television, where the manipulation itself became part of the weapon’s menace and display.
That display requires considerable skill. During opening and closing, the divided handles can pinch the fingers or strike the knuckles, and the blade repeatedly passes close to the hand. A flourish that looks effortless on screen may require extensive practice even when performed with a safe training blade.
Many butterfly knives have a small swivel latch that holds the handles together when the knife is closed. In theory, the same latch may secure them when the blade is open. In practice, it is difficult to engage in that position, generally requires the second hand, and it still may not hold the handles firmly together. The open knife should therefore not be treated as though it has a dependable locking handle.
There is an important difference between displaying a rehearsed opening flourish and using the knife during contact choreography. The ability to manipulate a butterfly knife attractively does not make its open handle secure or the prop fight-worthy. They are also very prone to breakage if accidentally dropped.
Converting a Switchblade Comb
A commercial switchblade comb may provide a useful starting mechanism when the audience must see a blade spring from the side of a handle. However, the spring is too weak to operate a replacement theatrical blade. The original comb must therefore be altered into something resembling a blade, rather than removed and replaced with one.
The completed conversion must remain light enough for the mechanism to operate safely. It must move freely through its full path, lock securely when open, and close without scraping or binding inside the handle. The conversion must not interfere with the button, lock, spring, or surrounding handle.
The small safety fitted to many novelty switchblade combs cannot be relied upon. It may move freely and fail to remain securely in either position. If it interferes with the mechanism, it may be permanently fixed out of the way—but the completed prop must then be treated as having no safety at all. Accidental opening must be prevented through its placement, handling, and rehearsal.
The finished prop remains a lightweight novelty mechanism. It should not be expected to withstand force, contact, or rough handling. And although the thin aluminum insert is not sharpened, its edge can still inflict a nasty cut much like the edge of a sheet of paper. It must therefore never be used for contact with a performer.
Mechanism Care and Repair
Keep pivots, tracks, locks, and sliding parts clean. Use lubricant sparingly and only when suitable for the mechanism. Excess lubricant can collect dirt and eventually make the action less dependable.
Inspect springs, buttons, catches, locks, pivots, fasteners, and blade play before every use. Do not increase spring tension merely to produce a more forceful or dramatic opening. Greater force also means a harder impact if the blade strikes a hand, costume, or nearby performer.
When a novelty automatic knife begins opening sluggishly, the spring is often blamed. In my experience, it has never been the spring. In practice, the cause is usually friction from dirt, damage, or compression of the thin metal handle. Repeated gripping, carrying, or dropping may press the sides inward until they rub against the blade. Cleaning and inspection may reveal the trouble, but a mechanism that remains unreliable must be removed from use.
Concealment, Drawing, and Deployment
A specialty knife must be placed so that it cannot open accidentally against the actor’s body or become entangled in the costume. Buttons and releases must be protected from unintended pressure, and the path of the opening blade must remain clear of fabric, fingers, and other objects.
The entire sequence must be rehearsed: reaching for the knife, drawing it, opening it, using it, closing it, and returning it to concealment. The actor must be able to control the prop without fumbling or looking down at it, but should never be encouraged to rush the action merely to appear skillful.
Boot concealment illustrates a common practical problem. The entire knife must be hidden, but only the blade becomes visible when it is drawn, as the handle is enclosed by the actor’s hand. A blade large enough to read clearly from the house may therefore make the complete knife too long or bulky to conceal comfortably and retrieve safely. The actor must be able to walk, sit, kneel, and perform the scene without the prop pressing uncomfortably against the leg—especially against the ankle bone.
Any concealed placement should be tested in costume and viewed from the audience—not merely judged while standing in front of a mirror. A knife that cannot be carried and drawn safely is unsuitable, however effective the reveal may appear.
Final Practical Rule
Use a specialty mechanism only when the audience must see that particular action. If the opening, unfolding, or transformation is not theatrically important, use a simpler and more dependable prop.
No mechanism compensates for poor selection, preparation, inspection, or rehearsal.