Stronger than "The Three Strings"! !!
The magician presents three strings of the same length, which he ties together. He wraps them in his hand. A magic pass (indispensable, the magic pass!...), the rope is unrolled... yes THE rope, because now the knots have disappeared, and we only have one long rope!
Extremely spectacular!
Other possible presentation : You can also start with three strings of different lengths, which become three strings of the same length; then the three separate pieces "mend" to form one single string!
Easy to execute.
The fake equipment does all the work for you!