And when Herod would have brought him forth, the same night Peter was sleeping between two soldiers, bound with two chains: and the keepers before the door kept the prison. Sleeping between two soldiers, bound with two chains - Two soldiers guarded his person; his right hand being bound to the left hand of one, and his left hand bound to the right hand of the other. This was the Roman method of guarding their prisoners, and appears to be what is intimated in the text.
Related Commentaries of Acts 12:6
Acts 12:6
6 And when Herod would have brought him forth, the same night Peter was sleeping between two soldiers, bound with two chains: and the keepers before the door kept the prison.