An ancestor tablet is a wooden board inscribed with a deceased relative's name, dates and status, sometimes built as an inner slip inserted into an outer casing, and in several regional traditions the calligrapher deliberately leaves a single stroke or dot incomplete when the tablet is first inscribed, a small omission that matters because completing it is itself a ritual act rather than a formality.
The dotting ceremony
That missing dot is filled in during a specific rite, dianzhu, performed by the eldest son of the deceased or by an invited Daoist or Buddhist priest, and this act, not the carpentry, is understood as the moment the tablet becomes the actual resting place for the ancestor's spirit rather than merely a labeled piece of wood.
Where it is kept, and what happens across generations
A completed tablet is kept on a household altar or in an ancestral hall and receives regular offerings, but individual tablets are not necessarily kept forever as living memory of the specific person fades across generations, some traditions retire an ancestor's individual tablet after several generations, combining the name into a collective tablet for more distant forebears, or ceremonially burning the old one, rather than keeping every ancestor's tablet separately without end.