Kelim, Chapter Twenty-One, Mishnah One
If a table or a side-board was damaged or he covered them with marble but room was left for cups to be set, it is unclean.
Rabbi Judah ruled: there must be room enough for pieces of food.
Section one: The mishnah describes two situations. The first is of a table or side-board (what we might call a counter) that was damaged. The second is of a table or side-board (both made of wood) that were covered with marble. Marble is not susceptible to impurity. In both cases, if enough of the table remains undamaged, or if enough remains uncovered with marble, for cups to be placed on the table, it is still susceptible.
Section two: Rabbi Judah says that space for cups is not enough. There must be enough space for pieces of food. If not, the table is not considered usable or is considered to be fully covered with marble, and it is clean.