The structure of calligraphy is regular-this rule was discovered and used by our ancients two thousand years ago, but it can't be said, so it can only be understood, not expressed. Later generations can only copy and look for their own feelings from the ancient penholder structure, which is called understanding. The most time-consuming thing is the shelf structure. If you find it, even if you practice calligraphy, you can't just copy it to find your feelings. We must find the law of calligraphy structure and study the calligraphy of the ancients with the law of calligraphy structure, so as to learn the root of calligraphy structure. If you are interested, you can see Zhou's discussion on the structure of calligraphy on Baidu.