a compass generally consists of a territory and a sky disk. There are straight needles, sewing needles and middle needles on the compass; There are gold plates and silver plates; There are inner disk and outer disk; There are three sets of heaven, earth and people. Some Feng Shui teachers use a positive needle to measure the sky, while others use a positive needle to make a dragon; Some use sewing needles to measure the ground, and some use sewing needles to determine the sitting direction.
There are many sizes of compasses, such as 6-inch, 8-inch, 12-inch, etc. Among them, the 6-inch compass with a diameter of 3.5cm in Tianchi is more common.