What does "using a pen" mean in calligraphy?

"Using a pen" in calligraphy refers to the way, method and effect of strokes. China's calligraphy is mainly stippling, and the tools used are mainly sharp pens. Therefore, it is very important to write and transport pens correctly. The height and thickness of the pen, the quickness and Fiona Fang of the pen, the concealment and smoothness of the nib, the length and thickness of stippling, the force and texture of brushwork and so on. All need to be realized with a precise pen. In Song Dynasty, Mi Fei called himself "pen", Cai Xiang called him "music", Huang Tingjian called him "painting" and Su Shi called him "painting", which vividly summarized the different methods of using pen.