Kelim, Chapter Twenty-Two, Mishnah Seven
1) A chair, of which two seat boards were removed, this one next to this one:
a) Rabbi Akiva says: it is susceptible to impurity;
b) And the sages say that it is clean.
2) Rabbi Judah said: so too if the seat boards of a bride’s chair were lost, though the receptacle under remained, it is clean, since where the primary function has ceased, the secondary one also ceases.
Section one: If two adjacent seat boards were removed, one of the side ones and the middle one, Rabbi Akiva still considers it susceptible to impurity. One could sit on the side seat board. The other sages say that this is no longer considered a chair, and therefore it is clean.
Section two: Rabbi Judah relates back to mishnah four. There Bet Shammai and Bet Hillel disagreed with regard to a bride’s chair whose seat boards were removed. Bet Hillel held that such a chair is clean. Rabbi Judah adds to this. The chair is clean even if the receptacle that they make under the chair to hold various things remained. Since the chair cannot be used in its normal fashion, for the bride to sit upon, the fact that it can be used for other purposes does not mean that it is still susceptible to impurity.