Explanation #1 (Rashi): Between two Chatzeros there is like a small Mavuy, and no residents open to it. The pit is in the space interrupting between them;

This one sticks out a ledge Kolsheu until the pit and draws [water] through its window, and so does this one;

Since it is distanced four, they do not have authority over it to forbid each other;

Also, because both have Reshus in the Mavuy, there is not [reason to forbid], for there are not residents open to it to go and come by foot. They use it only through air;

Implied question: According to letter of the law, we should not require even a ledge!

Answer: It is for a mere Heker (indication), lest they use another Reshus of two people without an Eruv. Therefore, they make a small Tikun here.

According to Rav, no Tikun is needed, for one does not forbid to his friend through air.

Question (Rashi, 85b): Regarding two houses and three ruins between them, the middle one is forbidden. We establish this when they are in a triangle, in order that the middle is totally forbidden, because each uses the four [Tefachim] next to itself, without air;

They should similarly forbid a small Mavuy [between them], since each uses the four Tefachim next to itself;

Since the Mavuy is forbidden, how can one lower [a bucket] and draw from the pit to the Chatzer through the air of the forbidden Mavuy?

Answer (Rashi): There is different. A ruin is used also nearby. Here, the only use of the Mavuy is drawing, which has a distance of four [Tefachim] in between.

Explanation #2 (Ri): The case is, this pit extends the entire length of the Chatzeros and interrupts between the four [Tefachim] next to this Chatzer and the four next to the other Chatzer. Each is considered a Reshus by itself.

Explanation #3 (Ri): The case is, the interruption between the two Chatzeros that the pit is there, is not Reshus ha'Yachid, rather, Reshus ha'Rabim or Karmelis, and Mechitzos of the pit are 10 tall;

When they fill from the pit to the Chatzer, they bring via above 10, which is Mekom Petur, like we say in our Sugya about two houses on two sides of Reshus ha'Rabim (85b). It is permitted to throw from one to another.

Explanation: [They use it like Rav Papa taught,] for hats and turbans.

Initially, [the Tartzan] thought that we discuss heavy loads. It is not common to bring them close to the walls, and they use the roof through throwing...

E.g. those who carry loads hanging from poles on their shoulders, and when they want to adjust the load, they adjust on the roof, and there are four Tefachim between the person and the roof.

[The Gemara] answered (rejected, that they use the roof) for hats and turbans, which is something light and common to bring it close to the wall. It is not through air [distanced horizontally].

Explanation #1 (Rashi): The ruins do not have owners, just the people of these houses.

Inference: He holds that if they have owners, the owners forbid them to the people of the houses.

Implied question: They do not forbid the Chatzer or Mavuy that opens to them, for we hold like R. Yehudah, that a storehouse for straw does not forbid (72b)!

Also below (86a), we rule like R. Shimon, who says that Dirah without owners is not Dirah!

Answer: In any case, in [the ruin] is forbidden to carry.

Support: Above (74a, Rashi) explicitly explained so regarding "perhaps he will come to take out Kelim of the houses to the ruin;

He explained that it is a different Reshus that has owners, and it did not join [in Shituf] in the Mavuy, for it does not forbid, like a Beraisa above (72b) teaches, that only a place of Dirah forbids, i.e. the place of bread or the place of lodging.

Implied question: Why do we permit here to use what is close to him? Even though his friend also has a share in it, he does not forbid this one!

Answer: Since also this one has a share in it, for both of them are partners in all three of [the ruins], and they do not forbid the close ones to each other, since for this one it is convenient use, and for this one it is difficult.

Regarding two balconies below (88a), if they made [a Mechitzah] for the bottom, they withdrew from the top, and they do not forbid the top, even though they made it in partnership, and they have a share in it.

Rebuttal (Ri): It is unreasonable to consider a Dirah without owners to be a Dirah only partially, to forbid carrying in it!

Explanation #2 (Ri): We said above (74a) perhaps he will come to take out Kelim of the houses to the ruin - that discusses a ruin open to the house;

We discuss when the house is open to another side, and is not regular in the Mavuy. Therefore, the Mavuy is not permitted through a Lechi or Korah due to the house, rather, due to the ruin;

We properly discuss ruins that have owners. Since they do not live in them, they do not forbid.

Explanation #1: Rashi's Perush is primary. It refers to the pit between two Chatzeros (85a). Shmuel holds that a person forbids to his friend through air, even though it is inferior usage;

[The Gemara] answers that there, the Reshuyos are mid'Oraisa, and there is no concern lest amidst this he come to carry from Reshus ha'Yachid to Reshus ha'Rabim, for people know an Isur Torah;

However, here, if they did not forbid each other, perhaps amidst this one will carry from Chatzer to Chatzer.

Explanation #2: R. Tam explained differently. It is not correct.

Explanation: [Did Rav say] that one cannot forbid to his friend through air? It was taught that two houses...

We are thinking that the reason one may not throw is because it goes through air of Reshus ha'Rabim above 10, and [Rav] says that the air of people of Reshus ha'Rabim forbids him, even though they have no use here. Also Rashi explained like this.

Explanation #1: We could not ask a contradiction in Shmuel, for the use through air here is not as important as that above;

However, according to Rav we ask from a Kal v'Chomer.

Explanation #2 (Rashi): We did not ask a contradiction in Shmuel, because he agrees about Reshuyos mid'Oraisa.

Reference: In Shabbos (97a) we establish it like this due to another question.

Question: Also there, it says "didn't we establish...?" (Each Sugya implies that we established it like this due to the question in the other Sugya!)

Explanation: [It is an Eruv] even if there is no straw there, for regarding placing an Eruv, we require only that it is proper for Dirah.

Implied question: It says above (72b) that a storehouse for straw forbids!

Answer: That is only when there is there straw, just like R. Yehudah holds that only a place of Dirah forbids, i.e. only when he dwells there on Shabbos, for we require a place of bread or a place of lodging;

This that it teaches here "one who lives there forbids him", this is only if the Ba'al ha'Bayis does not have straw there;

If he has straw there, it is as if he lives with him there in the house according to R. Meir, who considers a storehouse for straw like a place of Dirah (above, 72b), and they do not forbid each other.

Question: We find that Eruv is called Shituf, above (71a) - a Ba'al ha'Bayis who was a partner with his neighbors, with this one in wine, and with this one with wine, they need not be Me'arev, and below (91b) it says 'what does it mean "they were not Me'arev"? They did not do Shituf'!