What's a tau cross?

I'm always being asked this, and when I found this note from Sr. Julie Ann, I thought I'd re-post it here, since it was better and more concise than anything I could have written. (I've added the image and the links myself.)

Francis used the 'tau' in his writings, painted it on the walls and doors of the places where he stayed, and used it as his only signature on his writings.

The first recorded reference to the 'tau' is from Ezekiel 9:4, "Go through the city of Jerusalem and put a tau [cross] [mark (NRSV)] on the foreheads…"

The tau is the last letter of the Hebrew alphabet and looks very much like the letter 'T'.

At the Fourth Lateran Council, on November 11, 1215, Pope Innocent made reference to the tau and quoted the verse from Ezekiel. It is widely accepted that St. Francis was present and that he heard the words of Pope Innocent III when he said, "The tau has exactly the same form as the cross on which our Lord was crucified on Calvary, and only those will be marked with this sign and will obtain mercy who have conformed their life to that of the Crucified Saviour."

From then on, the tau became Francis' own coat of arms.

(With thanks to Sr. Julie Ann FSCC)