Kelim, Chapter Ten, Mishnah Four
1) If a ball or coil of reed grass was placed over the mouth of a jar, and only its sides were plastered, it does not protect unless it was also plastered above or below.
2) The same is true with regard to a patch of cloth.
3) If it was of paper or leather and bound with a cord, if he plastered it from the sides, it protects.
Section one: The reed grass does not offer an especially good sealant. Therefore, for it to protect he must also plaster either over or under the ball or coil. The jar is not considered tightly sealed if all he does is plaster its sides.
Section two: The same is true with a small patch of cloth (too small to be itself susceptible to impurity).
Section three: The paper or leather, bound to the jar with a cord, does not have holes (as does the reed grass and the cloth). Therefore, as long as he plasters from the side, the paper or leather protect the jar. [It would seem that their paper was probably far thicker and more durable than our paper].