It is well–known from the literature that the Romans crucified rebels and criminals. In 1968, an ossuary (bone box; see below) was found, among others, in a tomb in north Jerusalem in which were the bones of a 28-year-old man and those of a child.

This is a replica of a right heel bone of a 28-year-old man who was crucified in Jerusalem prior to its in AD 70. This replica is presented in the Israel Museum.
A 4.3-inch nail penetrated the right heel bone of the man. A piece of wood was placed on each side of the heel prior to the pounding of the nail to affix the person to a cross.

The skeletal remains of the man with the nail in his heel bone were found in this ossuary that was discovered north of Jerusalem.
Clearly visible is the Hebrew writing of the name “Yehohanan son of Hagkol.” Note the two clear lines. Above and to the right of the name “Yehohanan,” in the first line, is another faint inscription (click on image to enlarge to view inscription).
The above picture represents a scholarly reconstruction of how Yehohanan son of Hagkal was crucified. Note how his arms are tied to the cross—no nails were found in his hands or wrists. In contrast, Jesus of Nazareth’s hands were nailed to the cross—Thomas wanted to see the “mark of the nails in his hands” (John 20:25).
HaFor a convenient description of this find see pp 318–22 in Clyde E. Fant and Mitchell G. Reddish, Lost Treasures of the Bible — Understanding the Bible Through Archaeological Artifacts in World Museums. Grand Rapids, MI: Eerdmans, 2008.