'Chains' in the Bible

Now when Herod was about to bring him [out], on that [very] night Peter was sleeping between two soldiers, bound with two chains, and guards before the door were watching the prison.

And behold, an angel of the Lord stood near [him], and a light shone in the prison cell. And striking Peter's side, he woke him up, saying, "Get up {quickly}!" And his chains fell off of [his] hands.

Then the military tribune came up [and] arrested him and ordered [him] to be bound with two chains, and inquired who he was and what it was that he had done.