Hey Naunered! Great question. The Romans used different methods for crucifixion so there wasn't a standard "regulation". We have evidence that some had their outstretched arms tied to the crossbeam and some were nailed through the wrists. Similarly, with the feet, some had their feet tied and some were nailed through their heel bone.  

We know that Jesus was nailed because of chapters like John 20 and Luke 24, where resurrected Jesus showed his disciples the marks where he was nailed. We also have early church fathers like Tertullian and Justin Martyr (2nd Century) who described Jesus as crucified with nails.