Leak marks mean that strokes should be slow and even, and not vain.
Tapping the sand is like a sharp thing passing through the sand, and the traces left on both sides are the same, which means that it should be written in the middle.
Folding fork describes a strong and elastic feeling at the turning point.
On the other hand, Yin Yinni said that the pen should be used calmly, in all directions, and not with a sliding pen, which seems to have something in common with the leak marks.