A simple keychain made of two different sizes of curtain rings, yarn and a short piece of chain.
If you want to do it, just wind the yarn hard around the smaller curtain ring and tie the ends together when you reach the spot where you started. Use a thin needle to fasten the tails between the ring and the yarn wrapped around it. This was the tricky part but I only had to take the needle through about half a centimeter as it was so tight. In fact it was so tight I had to split each tail in two before I fastend them. Finish by taking the chain through both rings and join the ends.