What is Tonggen? What is thorough drying?

"Tonggen" means that the heavenly stems are connected with the roots. For example, the word "Ding" appears in the eight-character heavenly stems, "noon", "health" or "emptiness" appears in the earthly branches, and the fire of "Ding" is hidden in the heavenly stems, which is called Tonggen. The rule that the earthly branches seek their roots and enter Tibet is: the ugly child fails to get it at noon, and "through dry" means appearing in the sky. For example, the following eight words are "A", "C", "E" and "B". Day, month, day, day, day, day, day, night, night.