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]
(..) I've just handed you a murder inquiry. Five minutes in his flat. Four floors up. That's why they think they're safe. Put a chain across the door, bolt it shut, think they're impregnable. They don't reckon for one second that there's another way in. I don't understand. Dealing (..)2010 TvShow: Sherlock Title: The Blind Banker Season: 1 Episode 2