TAV is the last Hebrew letter and it is assigned to The World, Key 21. One of the meanings of this letter is mark or sign, as the sign of the cross, for example. And in Qabalah I often use the TAV, cross, form to create a quaternity that, like the number 4, helps us build a structure to our divination. Usually, four cards is all we need to know what Spirit is trying to let us know at any moment.
The number 4 is ubiquitious in Tarot: four worlds, four elements, four levels of awareness, sixteen (4 x 4) Court cards, 22 (2 + 2) Majors, etc.
Because I often use the TAV spread in divination, I have learned to use the TAV Tableau with the Majors also, to bring a new way of interpreting the twenty-two Arcana, in blocks of four that create five blocks, leaving both The Fool and The World aside, like a unit into themselves that brings 0 and 21, beginnings and endings, into the ourobouric cycle of eternity.
Work with one quaternity one day or week, or month at a time. Meditate on these five groups of four; allow the Fool and the World to come in and out of each quaternity, to create new associations, to build shadows and light. See what happens.