In Greek this verse is a continuation of the sentence begun with verse 17, but most translations, like Good News Translation, have a full stop at the end of verse 17 and begin a new sentence here.

It was customary for a condemned man to be either nailed or tied to the crossbeam with his hands spread out. Then the crossbeam was lifted into place on the vertical post. The man’s body rested on a peg attached to the vertical post, and the feet were either nailed or tied.

The persons crucified on either side of Jesus are not identified by John, but Matthew and Mark speak of them as “bandits” (Matt 27.38; Mark 15.27) and Luke as “criminals” (Luke 23.33). They are usually thought to be men who were arrested in the same revolutionary attempt in which Barabbas was taken prisoner.

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .