Using a pen like a cone to draw sand is the characteristic of Xiaozhuan.
Chu Suiliang said in "On Calligraphy": "The pen should be used like sealing mud, like a cone to draw sand, so that the edge is hidden, and the book will be calm. When the edge is used, it often wants to penetrate the back of the paper." For example, when drawing sand with a cone, the lines written with the center of the pen have a three-dimensional effect. Like an iron cone drawing a line on a plain surface, it is deep in the middle and shallow on both sides. When the center strokes, it is similar to the cone drawing sand. Drawing sand with a cone is a technique of using a pen. It was first proposed by Chu Suiliang, a calligrapher in the Sui and Tang Dynasties. It requires the tip of the pen to be hidden when writing, and the tip of the pen to be wrapped in stippling, just like walking in the sand with an awl. The tip of the awl is always in the middle of the line, and the same is true for the brush.
When writing Xiaozhuan, the writing technique is also required to use the pen in the center, just like a cone drawing sand. In this way, the lines of Xiaozhuan will be round and full. The essence of Xiaozhuan is similar to that of drawing sand with a cone, so using a pen like a cone to draw sand is the characteristic of Xiaozhuan.