The mud is the last ground before the crossing, and the caution attached to it belongs to the moment rather than to any fault in the line. A yang stroke here is correctly placed in an odd position by the standard rule, yet it sits at the top of the lower trigram, the position classical commentary treats as inherently exposed, since it is the point where one trigram's situation is about to give way to the next. That structural exposure is what produces the caution: correctness of position does not remove a danger belonging to the moment rather than to the line's own quality.
When this line changes, Qian's top stroke becomes yielding, turning the lower trigram into Dui, the joyous lake, while Kan remains above. The resulting hexagram is Number 60, Limitation, water over lake, an image of a lake that holds only so much water before it must be bounded, and whose Judgment ties success to limits that are not carried to a painful extreme. The line that stood at the most exposed edge of Waiting, closest to danger and most in need of restraint, transforms into a hexagram whose entire subject is restraint as a formal principle rather than an improvised response to a single threat. The movement suggests that the caution learned at the water's edge, once fully absorbed, becomes the more general discipline of knowing where any boundary ought to be drawn.