How Do You Know Which One Is the Cross of Christ?

The story of St. Helena finding the cross is actually, it actually comes from St. Ambrose. The Romans thought these things, these instruments of death are unclean and just what do you do with them? You dig a hole. And she has this act of faith to start digging. She strikes a piece of wood that would have been written Jesus, the son of Nazareth, King of the Jews. Then she discovers more wood and discovers three crosses. How is she going to figure out which one is the cross of Christ? Did they label it? Like this one was Jesus, this one was Dismus, this was Gorgon, or whatever the name of the bad thief was