(Mishnah - R. Meir): All roofs of the city are considered one Reshus (one may transfer between them if they are open to each other), as long as a roof is not 10 Tefachim higher or lower than the adjacent roof;

Chachamim say, every roof is a separate Reshus. (One may not transfer between them without an Eruv);

R. Shimon says, roofs, Chatzeros and Karfifos are all considered one Reshus for Kelim that were Shoves in them, but not for Kelim that were Shoves in the house.

(Gemara - R. Yosi bei R. Bun): Rav and Shmuel argued. Shmuel says [that all roofs are considered one Reshus] up to Beis Sa'atayim, Rav says that we carry in them even a [Beis] Kor or two Korim.

Assumption: When do R. Meir and Rabanan argue? It is when [the houses underneath] were Me'arev (then it is as if there are residents above, to forbid) but if they were not Me'arev, no (then all permit without limit - PNEI MEIR.).

Rejection: You can even say that they were not Me'arev. The case is, they all belong to one person. (Shmuel considers it like a Karfef not Hukaf l'Dirah.)

In our Mishnah, all ascend on a Tzuri (big) ladder or a Mitzri (small) ladder, but if all ascend on a small ladder and one on a big ladder, [only] the one on the big ladder is considered an opening, and the rest may ascend and descend [with him].

Question: (According to Rabanan, each roof is a Reshus unto itself - PNEI MOSHE.) May one carry in all of it?

Answer #1 (Shmuel): One may carry in all of it.

Answer #2 (Rav): One may carry only in four Amos.

Question (against Rav - Mishnah): If a wide roof is next to a narrow roof, the wide roof is permitted, and the narrow roof is forbidden;

Granted, the wide roof is permitted in four Amos. Is the narrow forbidden is four Amos?! Is there any Isur in four Amos?!

Answer #1 (Rav and Shmuel): [The Mishnah means that] we give to [the wide] four Amos in front of its opening [in addition to the usual four Amos. The narrow receives only four Amos.]

Answer #2 (R. Yosi bei R. Bun citing Shmuel): [The Mishnah discusses when the narrow roof is totally] open to [the wide] roof. Even so, the wide is permitted (Rav and Shmuel argue about how much), for it is not totally breached. The narrow is [totally] forbidden, for it is totally breached.