How are these [three fingerbreadths] measured? Rabban Shimon ben Gamliel says: The ruler is placed between [the feet] — [everything] from the ruler and outward is tahor [while everything] from the ruler and inward — including the place of the ruler — is tamei.

[Regarding] an oven that one partitioned with boards or with curtains, if the sheretz is found in one compartment, everything is tamei. [Regarding] a damaged basket plugged up with straw and hanging into the airspace of the oven, [if] a sheretz is in [the basket], the oven is tamei. [If] the sheretz is in the oven, [any] food that is inside [the basket] is tamei. But R’ Eliezer rules [it] tahor. R’ Eliezer said: If [the container] affords protection in the more severe [case of a] corpse, should it not afford protection in the more lenient [case of an] earthenware utensil? They said to him: If it affords protection in the more severe case of a corpse, that is because we can divide tents; should it then afford protection in the more le- nient [case of an] earthenware utensil, given that we cannot divide an earthenware utensil?