Also known as: The Ring Leader (metal rings version)
Aim: separate the 4 rings then put then back in place.
Comment: This puzzle is extremely complex. You should not “force” to get a ring through a rope (this would probably break your rope and, if it was the way to go, this puzzle would be meaningless!).
Solution: See the Quatro solution (WARNING, by looking the solution you’ll loose all the fun and pride that self-solving it always brings!)