The basic method of writing square points is to reverse the front face to the left, slightly reverse the front face to the right, take the pen collection as the center, slightly lower the pen to the right, and then return the pen to the front face to the left.
The point on the right pointed by Liu Zi has different lengths, such as "Ran" in Shence Army Monument:
The point above is relatively short, so you don't need to go straight in the middle. This is the way of writing:
The last three points below are all relatively long, especially the last one. The middle stroke is a bit like writing "Shu". After a short stroke, you can't let the pen tip "sweep" down to the right. You must go straight to the paddling with it as the center, and then gently lift the folding front to the left.
Note: Everything is abrupt and frustrating, only inadvertently, otherwise it will be polluted by accumulated ink. Practice makes perfect. The points of willow characters are not fixed, but varied and need to be understood carefully.