The Tau cross (which can be pronounced to rhyme with "gnaw" or with "now") is not seen frequently. The Tau cross is in the shape of a capital “T,” and is named after the Greek equivalent to the English letter “T.” The Tau cross is thought to predate even the Latin cross, and is sometimes called the “Old Testament cross.”
It is also sometimes called the Cross of St. Anthony, and there are several legends around the connection of Anthony to this Cross. If you are curious about them, let me know and I will add them to this site.
You'll have to keep your eyes open to find this symbol as it is not used often. I have personally seen more Tau crosses in the form of wall crosses than in two dimensional depictions (stained glass, painting, digital projections).
You may be able to find the Tau cross incorporated into other symbols, such as depictions of the Trinity. See the Trinity Shield for more discussion on depictions of the Trinity.
It is also sometimes found (in various forms) in depictions of St. Anthony.
Read Numbers 21 and then John 3.14. The passage in John compares the crucifixion of Christ with the bronze serpent that Moses lifts up in the wilderness. Tradition tells us that the pole on which Moses lifted the serpent was a Tau cross. As this event from the life of Moses seems to anticipate the crucifixion of Christ, this cross is sometimes called the “anticipatory cross.” Read both passages, and highlight the ways in which the Numbers story does or does not reflect your understanding of the Crucifixion.
If you're in the rare position of having a Tau cross depicted somewhere in your worship space, or are bold enough to display one either digitally, on a bulletin, or some other way, it could be an excellent opportunity to highlight your atonement theory, or to draw comparisons between the passages mentioned above.
As with any the symbols on this site, its use (or in this case, more likely its neglect!) is up to you. However, the Tau cross would lend itself easily to use to use during lent, with its focus on anticipating the crucifixion.