What structure is used for the joint of the head and the back legs of the Nanjun hat chair?

Digging tobacco pot. Digging pot structure is a traditional mortise and tenon structure, mainly used for chair armrests, wooden comb back chair and back chair hitching part, as well as round furniture frame group structure. In the South Hat Chair, the joint between the head and the back leg adopts the dugout structure, which can realize a solid connection and keep the appearance simple and beautiful at the same time.