And the Lord said to him: Go through the midst of the city, through the midst of Jerusalem: and mark Thau upon the foreheads of the men that sigh, and mourn for all the abominations that are committed in the midst thereof.
The “tau” or T-shaped cross is mentioned in the Old Testament and is seen as a foreshadowing of the Cross of Christ.
At least one of the ancients believed the Tau to be the form of the Cross of Jesus. Tertullian wrote, “The Greek letter and our Latin letter T are the true form of the cross, which, according to the Prophet, will be imprinted on our foreheads in the true Jerusalem.” (Contra Marc., III, xxii)
On a practical note, some scholars have suggested that since crucifixions were a common and repeated practice in the Roman world, the T-shaped cross (with a cross bar that would have been carried and attached to the victim and then hoisted to the top of a permanently planted upright member) might be a more authentic rendering of Christ’s cross.
32 Two others also, who were criminals, were led away to be put to death with him. 33 When they came to the place that is called The Skull, they crucified Jesus[e] there with the criminals, one on his right and one on his left.
When I survey the wondrous cross
On which the Prince of Glory died
My richest gain I count but loss
And pour contempt on all my pride. Amen