Acts 12:6. Peter was sleeping between two soldiers, bound with two chains.
Among the Romans the prisoner was bound to the soldier who had charge of him by means of a chain, which joined the prisoner’s right wrist to the left wrist of the soldier. Sometimes, for greater security, the prisoner was chained to two soldiers, one on each side of him. This was the case with Peter. Paul was at one time bound in a similar way. See Acts 21:33. At another time he was fastened to a single soldier. See Acts 28:16, 20.