Carrying the shoulder horizontally refers specifically to the writing method in regular script fonts where the right side of the horizontal stroke is slightly higher than the left side. This is a basic feature of horizontal strokes in regular script.
We all know that writing should be "horizontal and vertical", but those who have learned a little bit of calligraphy will find that there are almost no true horizontal and vertical characters in the ancients' writing. For example, the word "Xuan" in the thirteenth line of Wang Xianzhi's "Luo Shen Fu" above is tilted almost 30° in length and width.
The vertical lines represent life, dignity, eternity, power and the ability to resist change. Horizontal lines tend to represent silence and tranquility, the calmness of the sea, death, earth and sky. Slash means action, danger, collapse, uncontrollable feelings and movement.
In photography, horizontal lines imply a sense of horizon, so they are stable and lack change. Reflected in calligraphy, just like computer calligraphy, strictly horizontal horizontal lines will appear rigid.
To break this rigidity, calligraphers will tilt the horizontal lines upward to give people a lively psychological suggestion, just like using diagonal lines to compose pictures in photography.
Extended information:
When human eyes look at objects, they always instinctively follow the order from left to right and top to bottom. This order has no meaning. Doubts will affect the viewer's psychological feelings about the picture.
Slanting to the upper right will give people a positive psychological hint of rising.
If it is written to the lower right, it means a negative ending, which instantly leads the vision to the end.
So in order to break the mediocre feeling of "horizontal", calligraphers tilted it upward to the right, making it more lively.