From "Sui Shu Jing Ji Zhi Yi": "The Han Dynasty taught children six styles, such as ancient prose, variant script, seal script, official script, Miao seal script and insect bird, and more than 20 trends, such as calligraphy, regular script, hanging needles, hanging dew and flying white, all of which were based on the later six books and changed with events."
The hanging needle vertical mainly describes that the vertical painting is long and straight, and the end is as straight as a needle. Sometimes it is also used to describe something or a person standing straight. It has also been extended that the situation is more dangerous and unstable, such as the imminent threat from the enemy, and the danger is like a pile of eggs.