Inspired by a theatre company’s request for retractible knife recommendation:
In fight direction circles for stage, retractible knives are generally considered extremely dangerous and unnecessary. It’s one of those things, like contact slaps, that most people don’t see how it could go wrong until it does. I know of a production of Julius Caesar, wherein the actor playing Caesar was stabbed in the lung by a retractible knife when the spring mechanism failed. The retraction didn’t happen, and therefore the retractible knife became a real knife (the actor lived). There are many techniques one can do with a blunt solid steel knife that will provide an equally good illusion, thus improving your audience’s experience, and will be immeasurably safer, thus improving your actor and stage manger’s experiences.  If there are stabbings in your stage production, seek out a fight director and have them show you these techniques.
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