What is a tee? When was it put forward?

The three links of literature refer to Du You's General Canon in Tang Dynasty, Zheng Qiao's General Annals in Song Dynasty and Ma Duanlin's General Examination of Literature in Yuan Dynasty. The "three links" in cross-strait relations refer to "postal, air and trade links", that is, "big three links". Starting from 200 1 1, the Taiwan Province authorities opened the direct exchanges of goods and people between Jinmen and Mazu and Fujian coastal areas in stages, which is the so-called "mini three links". Tees can also be interpreted as pipe fittings and pipe joints. Also known as pipe fitting tee or tee, pipe fitting and tee are used in the main pipeline to be branched.