כיצד משערין אותן

How was this (the airspace between three pegs that protruded laterally from a kirah) measured?

Rabban Shimon ben Gamliel says:

one places the ruler between them (i.e. one draws a straight line from one peg, at the point that is three fingerbreadths laterally from the body of the kirah, to the same point on the next; when done with all three, this forms a triangle)

from the ruler outward (i.e. inside the triangular area demarked by the lines drawn with the ruler)

is tahor;

from the ruler inward,

and the space occupied by the ruler,

is tamei.

פרק ח משנה א

תנור

A tanur

that [had its interior] divided with boards

or curtains,

if a sheretz was found in one place (on one side of the partition)

all of it is tamei (on either side of the partition).

A round basket (made of straw or reeds)

that was missing a part of it (and so is no longer considered a utensil),

and [that void] was stuffed with straw (which is insufficient to restore its status as a utensil),

and was suspended into the air of the tanur (but the mouth at the top of the basket was at or above the top of the tanur),

[if a] sheretz is inside it [the basket]

the tanur is tamei (as the walls of the basket, which was not a utensil, does not shield it);

[if] the sheretz was in the tanur,

foods that were inside it [the basket] are tamei;

and Rabbi Eliezer rules it is tahor (with respect to the cases involving the basket in the oven).

Rabbi Eliezer says:

if it protects in the case of a cadaver (where a similarly damaged basket lies halfway inside a house containing a corpse, with the baskets' mouth lying outside the house, the contents of the basket will not become tamei)

which is more stringent,

should it not protect in an earthenware utensil that is more lenient [when it contains a mere sheretz]?

They said to him:

If it protects by a cadaver which is more stringent,

that is because we divide canopies (and those partitions are effective in blocking the spread of tumah),

should it protect by earthenware utensils that are more lenient

[even though] we don't divide earthenware utensils?