What is the 7% stop-loss rule?

Can you please explain to me in simple terms what exactly is the 7% stop-loss rule? I've heard it mentioned a few times in relation to cryptocurrency trading but I'm not entirely clear on its significance and how it can help traders manage their risk effectively. Is it a rule of thumb that should be strictly adhered to or is it more of a guideline? I'm interested in learning more about how it works and how it can be incorporated into my trading strategy.