Uncle, I have a problem

last night, my nephew from Warsaw (the youngest son of my brother in law) gave me a call, (via SIGNAL INstant Messenger)

He said: Help me please, the chain of my roadbike (Cannondale R1000, Shimano Ultegra) makes a lot of noise. I don’t know what to do.

I asked: OK, what did you do with the chain? Did you open it?

He: Yes, I opened it for cleaning and put it together in the right order.

I: I guess not, it looks like, you made at least a little mistake. Please turn your camera on and show me the part around the rear derailleur. (I already had an idea, whats wrong)

he showed me the derailleur and, well, thats just almoust not visible, but the lower part of the derailleur has a little hook, the chain must be threaded in the right way. there were just two options, they look very similar. if you choose the wrong one, the chain will stay on that hook every single chain link and gives a sound.

I showed him two fast drawings:

And well, the boy is very smart. He immediatly recognized the right one as the current status and knew what to do. 30 minutes later, he had solved the problem. All good!

Hier in diesem Bild sieht man es auch:

https://eu-browse.startpage.com/av/anon-image?piurl=https%3A%2F%2Fwww.mtb-news.de%2Fforum%2Fattachments%2F1588745146840-png.1036039%2F&sp=1620736777T6f9a7390754bf9f6fb8a86241c8f6082c1c737dd49453d572f41ddd030e3d643