The pattern
Hold 1-1-1, 2 through 8 once each, and 9-9-9 in a single suit. Any further tile of that suit completes a winning hand. When you hold exactly the thirteen-tile base, you wait on all nine tiles of the suit — the "pure" nine gates.
Why it is so rare
The hand requires a complete, concealed one-suit hand of a very specific shape. Statistical studies of online play suggest it appears only in tiny fractions of hands.
Superstitions
Japanese players joke that completing nine gates uses up a lifetime's luck. The story is told often, but the hand itself is simply rare.
Practical play
Nine gates is never planned from the start. It emerges, occasionally, from full-flush hands, so players pursuing a flush should keep an eye out for the shape.
