The year before last, when I was drinking coffee in a coffee shop, the cup and saucer were made of ceramic, which were very slippery between each other. I found that the cup moved left and right on the plate and saucer when the customer served the coffee, which caused the coffee to spill, which was very inconvenient.I have been thinking for a long time, thinking of the tenon and mortise fixation principle of the traditional Chinese wood craft, but it is difficult and not beautiful to use in the ceramic forming process. After countless days and nights of thinking, since the cup is liquid.