In my local climbing gym, I recently noticed this on the belay end of the just about every top rope. Pretty crafty! It’s not a tip for an everyday climbing situation, but hey, it might come in handy.
If you want to make a stopper knot semi-permanent, one way to do it is to run a zip tie through the knot and crank it down. The knot will be pretty much impossible to untie without cutting the zip tie.
Top roping with beginners all day and you want to be sure the rope system is “closed”, by always having a knot in the end of the rope?
Who else might have a need for this?