Center, also called forward. Is to let the pen tip run in the middle of the strokes when using the pen. As Cai Yong said in "Nine Potential", "Make the pen heart always move in stippling". With a pen in the center, the ink drips along the tip of the pen and penetrates evenly into the paper, so that the strokes avoid the problems of being heavy on the top and light on the left and right, and the two sides are like dividing lines, showing balance. The words "scraping sand with a cone", "Yin Yinni" and "leaking marks" mentioned by the ancients are metaphors of the effect of the central pen. Calligraphers have always advocated "centering pen and ink", which shows that centering is the most important brushwork of calligraphy.
Deflection, also known as flank. It means that the pen tip is biased to one side of the stroke when lifting the pen. The strokes written by Pianfeng are full and smooth, but not dry. Calligraphers have always believed that partiality is a drawback of calligraphy, but it cannot be generalized. Sometimes the edge of the book is exposed, sharp and lively, which makes the book more vivid.