Protesters formed 'a human chain' [=they stood next to each other with their arms linked] around the ancient tree to prevent it from being cut down.
In the United States, the President as the commander in chief is at the head of the military 'chain of command'.
I thought he really won the lottery but he was only 'pulling my chain'. [=he was only playing a joke on me]
(..) from the Lord Commander. - He wants me to... - I read your letter. You're to be a maester. Yes. And once I have my chain, I'll return to Castle Black. I thought the Night's Watch might make a man of you. Something resembling a man at least. You managed to stay soft and fat. (..)2016 TvShow: Game of Thrones Title: Blood of My Blood Season: 6 Episode 6