From Hexagram to Gate
Each of the 64 hexagrams becomes one of the 64 Gates on the BodyGraph, and the hexagrams are laid around the outer ring of the Rave Mandala in a fixed sequence. When a planet sits in a hexagram's slice of the wheel at the moment of birth, that Gate is activated. The Gate keeps the hexagram's number and a theme drawn from it, so Gate 1 carries the hexagram of the Creative, Gate 2 the Receptive, and so on through all 64.
Six Lines, Six Flavours
A hexagram has six lines, counted from the bottom up, and each line describes a different way its theme plays out. Human Design keeps this structure exactly. Every Gate has six Lines, which is where the Line numbers on your chart come from: a planet in Gate 34 Line 3 is sitting in the third of that hexagram's six segments of the wheel. The same six positions, generalised, give the six Line themes of the Profile, from the Investigator in Line 1 to the Role Model in Line 6.
The Genetic Parallel
The reason the I Ching sits at the heart of the synthesis is a pattern that was noticed after the genetic code was cracked in the 1950s. DNA is written in four chemical letters, read three at a time, which gives 64 possible three-letter words, the codons. The I Ching also has 64 figures, each built from two three-line groups, the trigrams, drawn from a binary pair of yin and yang. The two systems share the same underlying arithmetic. Human Design reads that match as the key, and the hexagrams as a thematic language for the imprint written into each person's biology.
What Is Kept and What Is Left
Human Design does not use the I Ching for divination. You do not throw coins or consult the oracle. Nor does it lean on the philosophical commentary that grew up around the text over the centuries. What it keeps is the wheel of 64, the six-line structure, and the sense that each figure describes a distinct quality of energy with its own light and shadow. Ra Uru Hu wrote a fresh set of descriptions for every one of the 384 lines, called the Rave I Ching, and it is that text, rather than the classical Chinese one, that the Gate and Line pages in this Knowledge Base are grounded in.