Six in the fourth place, as a changing line, is the hinge of the entire hexagram. It is the one yielding line among five yang lines, the small force that gives Small Taming its name, and its message is that sincerity rather than strength is what allows restraint to hold without provoking the danger of open conflict. A reading on this line concerns exactly that kind of position, holding back something much larger than oneself, and succeeding only because trust rather than force is what is offered.
Flipping this single yin line removes the only restraint the hexagram contains. All six lines become yang, and the result is Qian over Qian, pure and unmixed, the hexagram called The Creative. Nothing else in this small slice of the sixty four hexagrams turns on so complete a reversal from a single change: the entire structure of small holding back great simply ceases to exist, and what remains is unchecked creative force with nothing left to restrain it.
Within Small Taming's own movement, the fourth line is the pivot between the untroubled lower trigram and the ruling fifth line above it, the exact point where restraint is applied. A reading that falls here points to a moment when the whole situation depends on this one small, sincere check holding, and its transformation shows plainly what happens the instant that single check is removed.