(Mishnah): If a window between two Chatzeros is four by four [Tefachim] and within 10 Tefachim of the ground, the Chatzeros can be Me'arev individually or together;

If it is less than four by four or higher than 10 Tefachim, the Chatzeros can be Me'arev individually, but not together.

(Gemara): Bars [in a window] diminish [its width] regarding Shabbos (if it is four wide, they are Me'arev one. If it is less than four, they are Me'arev two), but they do not diminish regarding Chazakos (if one has a window four wide opposite his neighbor, the neighbor cannot build a wall that will block light and wind from it).

Straw and stubble do not diminish. Earth and pebbles diminish.

(R. Yosi bei R. Bun): If grass started growing in it, it does not diminish.

Question (to R. Aba): What you say about a window between two Chatzeros - does the same apply to a window between two houses?

R. Aba told them "yes''. They asked him if a window between two roofs [is the same], and he told them "yes''.

Question: [If the roofs of two houses are adjacent without a wall in between,] may one be Me'arev through the Lulim (openings in the roof between each house and its roof)?

Answer (Rav Avmari): Rav and Shmuel argue about this. A Mishnah there teaches that all roofs of the city are one Reshus;

Shmuel said, one may carry up to Beis Sa'atayim (like a Karfef not Hukaf l'Dirah. Therefore, one cannot be Me'arev it with the house below). Rav said, one may carry even a [Beis] Kor or two Korim (it is considered Hukaf l'Dirah, so one can be Me'arev it with the house below - NO'AM YERUSHALMI).

This is not only when all four by four [Tefachim of the window] are within 10 [Tefachim of the ground]. Rather, even if part of the four are within 10, it is as if all four by four are within 10.

Question: If [the window's] perimeter was 96 Tefachim (each side is four Amos, how much must be within 10)?

Objection: [This is obvious! Even if each side is only four Tefachim, we said that] if any amount was within 10, it is as if all four by four are within 10!

Clarification of Question: If [the window] was round, and the perimeter was [96 Tefachim, i.e. the diameter is four Amos, how much must be within 10? We cannot learn from a square window, for there, if any amount is within 10, a width of four Tefachim is within 10. If Mashehu of a circle is within 10, a width of only Mashehu is within 10. This question is not answered. This is our own explanation; it was inspired by PNEI MEIR and HA'GAON RAV C. KANIEVSKY, SHLITA.]

Question: (The Seifa of our Mishnah taught that if the window is higher than 10 Tefachim, they are Me'arev individually, but not together. Can we diminish [the height] through Kelim [left on the ground under the window, and measure the height from the Kelim]?

Answer #1 (R. Chiya bar Ashi): We can diminish through Kelim.

Answer #2 (R. Yonah citing R. Yitzchak bar Tavlei citing R. Yochanan): We do not diminish through Kelim.

Remark: There (in Bavel) they say that R. Chiyah Rabah and R. Yishmael bei R. Yosi [argue about this] - one forbids and one permits;

The one who forbids, this is lest he forget and move the Kelim (this would invalidate the Eruv).

R. Yochanan bar Maryei ruled to put wood or rocks (underneath; one may not move them on Shabbos).

(Beraisa): We may diminish with anything - with rocks, bricks and a Mitzri ladder (it is small, i.e. less than four rungs); this is only if he fixed it in place (with nails).

(R. Ba citing Rav Yehudah): It is even if he did not fix it in place.

Question (Beraisa): This is only if he fixed it in place.

Answer: R. Ba [explains that the Beraisa means that] he designated it [to be there permanently].

R. La ruled like [the simple reading] of this Beraisa. [It diminishes] only if he fixed it in place.

R. Yonah and R. Yosah both [said the same law], one in the name of Mar Ukvan, and one in the name of Rav Nachman bar Yakov. There must be between one rung and the next less than three [Tefachim]. It must be four Tefachim wide. The sides [of the ladder, which hold the rungs] complete [the Shi'ur] of four. (MEICHAL HA'MAYIM says that we must discuss when there is place to step on the sides, or the text should say "do not complete four.'')

(Yosa): A big rock in which steps were carved out, it diminishes. In any case, the sides [if they were not carved out, and they are above 10] do not complete 10 [to make it considered a wall. The sides are Batel to the top step] it is considered like a thick step. (We explained this like MEICHAL HA'MAYIM.)

(R. Yosa citing R. Bun bar Kahana): [The bottom of the steps] must be distanced four Tefachim from the wall, enough distance [to be easy to ascend].

(R. Chizkiyah citing R. Bun bar Kahana): [We do not require this for all the steps, just] the step that diminishes the 10 (i.e. the lowest step less than 10 below the window or the top of the wall) must be distanced four Tefachim from the wall, enough distance.

Question (R. Yakov of the south): [A Beraisa teaches that] if one brought a wall seven and Mashehu Tefachim, and raised it less than three [Tefachim] above the ground, it is permitted [to use it for a wall, due to Lavud. Also] there you say that any [gap] less than three, it is as if it is sealed;

And here you say that any [window] less than four [wide does not join Chatzeros, for] it is as if it is sealed!

Question: (This is not difficult. If a window is less than four, it does not join Chatzeros, for it is not an opening, even though it is not considered sealed.) If you want to ask, the following!

[Why does the Beraisa discuss a wall seven and Mashehu Tefachim? Even if] he brought a wall four and Mashehu Tefachim, and raised it three Tefachim less Mashehu [and fixed a rope 10 above the ground, this should make a Mechitzah]!

Answer: [The Beraisa] is like R. Yochanan said. The Omed (Chulyas ha'Bor) and the cavity (pit) join [to a width of four to make Reshus ha'Yachid]. This is if the Omed exceeds the cavity. (Here, the rope is less than the gap below it and the air above it. We explained this like HA'GAON RAV C. KANIEVSKY, SHLITA.)