How is the hollow surface made?

The hollow surface is as thin as hair, but the hole in the middle runs through the top and bottom, and it won't rot in the pot for a long time, so it is soft and firm.

When making, the refined flour is mixed with proper amount of oil and salt, kneaded into thin strips, put sticks on both ends to make the oil and salt fully penetrate, then hung on an elevated frame, and the noodles are slowly pulled down to a certain extent with both hands to form a hollow surface, then let it fall naturally, and only the middle gap part, that is, the hollow surface, is taken in the sun. The production method depends entirely on the skill of manual operation.