When someone has just passed away, we place a bowl of rice at their feet with a pair of chopsticks standing upright in it. Some families add an egg. This is called foot-end rice (脚尾饭).
It is a custom handed down from southern Fujian (Minnan). Records of Minnan funeral customs describe a bowl of plain rice with bamboo chopsticks standing in it, placed by the feet of the deceased, called “offering the foot-end rice”.
The chopsticks must stand upright, never lie flat. It shows that this rice is not for the living. It is for the deceased to take on the road.
The elders say the road after death is not easy. Have a bite to eat and put on good shoes before setting off.
It is not only rice at the feet. In Minnan custom, a lamp is also lit by the feet to light the way, and the family burns paper money there, called “burning foot-end paper”. Rice, light and paper: all so the deceased does not set off alone, hungry, in the dark or lacking anything.
So if your grandmother scolded you as a child for sticking your chopsticks upright in your rice, it was not about manners. That gesture is only made when sending someone off.
Chopsticks standing in rice look just like joss sticks in an incense burner. Doing it at the dinner table is like making an offering to the dead, which is why elders get upset.
No one may ever have explained this to you. Customs differ from place to place and between dialect groups, and this is shared for reference only, with no need to be superstitious. If there is anything else you would like to know, just ask us.