Light finger tapping is a custom for thanking the tea master or tea server for tea. After a person's cup is filled, that person may knock their bent index and middle fingers (or some similar variety of finger tapping) on the table to express gratitude to the person who served the tea. [1] Although this custom is common in southern Chinese culture such as the Cantonese, in other parts of China it is only acceptable if for some reason you cannot actually say thank you at that moment, for example if you are in the middle of talking with someone else at the table.