Interestingly the 2 links to 2 suppliers that Harry has given appear to show exactly the same trick with the same ropes but one supplier is selling it at half the price of the other.
For kids, with say a candy bar in the knot, I can maybe see this playing ok... especially if the ‘lucky’ kid chooses which one they want and you remove the other ropes for yourself leaving the ‘lucky kid with the prize. Or alternatively with something ‘unpleasant’ in the knot with you getting left with it and the kid(s) avoiding it. But you’d have to carefully script this or routine it with other effects to make it look like an actual trick and not just a 1 in 3 bit of luck.
That said, as a stand alone effect, to my mind, the magical deneumont hardly seems to be worth even the tiny effort and time that this takes to perform. :hmm: