[For the YouTube version of this topic, please click this tab.]
Are Retractable Knives Safe for Stage Use?
No.
Retractable knives (also called collapsible knives) are among the most dangerous props ever introduced into theatrical combat. They fail unpredictably, have caused serious injuries, and are considered unsafe by most experienced fight directors, weapons specialists, and insurance carriers.
If a director has requested a retractable knife, or a script specifically mentions one, it is important to understand that these props are not considered safe for stage use. Reality is under no obligation to conform to anyone’s opinion on the matter.
How Does a Retractable Knife Work?
A retractable knife contains a floating blade rather than a fixed blade. Inside the hollow handle, a shortened tang is surrounded by a compression spring. When the tip of the blade is pressed against something, the blade retracts into the handle. When pressure is removed, the spring pushes the blade back into place.
In theory, this creates the illusion of a stabbing action.
In practice, the system depends on the blade moving perfectly every time.
Why Are Retractable Knives Dangerous?
The danger occurs when the blade fails to retract properly.
Sometimes the blade catches against the edge of the handle opening. When this happens, the blade may remain partially extended while the user believes it has collapsed. The result can be exactly the opposite of what the prop was designed to accomplish: an actor can be stabbed by a knife that was supposed to be “safe.”
This is not a theoretical concern. Serious injuries have occurred when retractable knives malfunctioned during performance.
Haven’t They Been Used Successfully?
Yes.
Thousands of performances have been completed without incident.
The problem is not that retractables fail every time. The problem is that they fail unpredictably. A device that works correctly ninety-nine times and then fails catastrophically on the hundredth attempt is not suitable for theatrical combat.
What About Insurance?
Many insurance carriers view retractable knives as evidence of an unsafe work environment. Some carriers will refuse coverage for productions using them, even if an eventual injury has nothing to do with the knife itself.
The liability risk is simply considered too great.
Can a Retractable Knife Be Made Safe?
No.
A retractable knife cannot be made safe through better choreography, additional training, maintenance, modification, or redesign. The danger arises from the basic operating principle of the device itself.
For that reason, experienced theatrical weapons specialists generally recommend that retractable knives never be used in performance.
What Should a Theatre Do If It Owns One?
Destroy it.
I recommend immediately removing any retractable knife from stock, whether metal or plastic. No production benefit justifies the risk.
(modified and reprinted from The Textbook of Theatrical Combat. All rights reserved.)