What is the making method of Feng Shui compass?

Tianchi, also called the seabed, is a compass. The Tianchi of the compass consists of thimble, magnetic needle, submerged wire, cylindrical outer box and glass cover, which are fixed in the center of the inner disk. There is a sharp thimble in the center of the bottom surface of the round box, and a concave hole in the center of the bottom surface of the magnetic needle, and the magnetic needle is placed on the thimble. The arrow of the compass points south at one end and north at the other.

There is a red line at the bottom (seabed) of Tianchi Lake, which is called the submarine line, and there are two red dots on both sides of the northern end. When in use, it is necessary to make the northern end of the magnetic needle coincide with the seabed line.

Modern compasses mark the crosshairs on the seabed. When in use, the northern end of the magnetic needle should point to the northern end of the reticle, and the magnetic needle should coincide with the north-south line of the seabed.

The inner disk is a rotatable disk next to the outside of the compass. Many concentric circles are printed on the inner disk, and one circle is called a layer. Each floor is divided into different equal parts. Some floors have more squares, while others have fewer squares. The least floor is divided into eight squares, and the most floor has 384 squares. Different characters are printed on each grid. There are many kinds of compasses, some with many layers, some with few layers, the most with 52 layers, and the least with only 5 layers.

The outer disk is square, which is the tray of the inner disk. There is a small hole at the midpoint of the outer side of the four sides, and the red line penetrates into the ten meridians of Tianxin, which is used to read the contents of the inner disk. The ten directions of Tianxin are required to be perpendicular to each other, and the new compass you just bought must be calibrated before use. Some compasses, especially those made in China, have no outer disk and are inconvenient to use. Most of those sold abroad were produced in Hongkong and Taiwan Province Province in modern times.