Quote from : Slaughterhouse-Five Book

...Jesus was only twelve years old. Jesus was learning the carpentry trade from his father. Two Roman soldiers came into the shop with a mechanical drawing on papyrus of a device they wanted built by sunrise the next morning. It was a cross to be used in the execution of a rabble-rouser. Jesus and his father built it. They were glad to have the work. And the rabble-rouser was executed on it. So it goes.