(Mishnah): If one was reading a Sefer [of rolled up parchment] on a porch and it became unraveled (he is holding one end, and the other end fell off the porch to the ground), he may roll it back to himself;

If he was on the roof (Reshus ha'Yachid) and it became unraveled - before the end comes within 10 Tefachim of the ground (Reshus ha'Rabim), he may roll it back;

Once the end is within 10 Tefachim, [he may not roll it back. Rather,] he turns it over on the writing (lest it be seen, and Kisvei ha'Kodesh are disgraced).

R. Yehudah says, even if the end is a tiny amount above the ground, he may roll it back to himself;

R. Shimon says, even if the end is on the ground, he may roll it back, for we do not enforce any Shevus (mid'Rabanan law) if this will cause disgrace to Kisvei ha'Kodesh.

(Gemara) Question: Our Mishnah discusses a porch that is permitted (Mekom Petur). It is forbidden [to take the Sefer] outside the porch (one may not transfer from Reshus ha'Yachid to Reshus ha'Rabim via Mekom Petur! The Mishnah connotes that he was holding it outside the porch when it became unraveled.)

Answer #1: He was sitting and reading in [the Sefer, on the porch] during the day (Erev Shabbos).

Answer #2: He forgot and took it out. (We explained this like YEFE EINAYIM 98a.)

(Mishnah): Before the end comes within 10 Tefachim of the ground, he may roll it back to himself. Once [the end] reached within 10, it is forbidden.

(R. Yakov bar Acha citing R. Yosa): This is like R. Yehudah, who forbids using the airspace of 10 Tefachim [above Reshus ha'Rabim, even if it is not at rest, for Kelutah k'Mi she'Hunchah (he considers it to be at rest).]

(Mishnah): Once the end is within 10 Tefachim, he turns it on the writing.

What is the reason? It is lest the writing be disgraced.

This is like R. Acha said in the name of R. Shmuel bar Nachman. A Sefer [from which he was learning, or he was writing it and needs to let the ink dry] that he has no cloth with which to cover it (lest dust come on it), he turns it on the writing, lest the writing be disgraced. (We explained this like HA'GAON RAV C. KANIEVSKY, SHLITA.)

(Mishnah - R. Yehudah): Even if the end is a tiny amount above the ground, he may roll it back to himself.

Contradiction: R. Yehudah contradicts himself! There he forbids using the airspace of 10 Tefachim, and here he says so?!

Answer (R. Yochanan): This is not R. Yehudah's opinion, rather, R. Meir's. R. Yehudah [taught] Chachamim's opinion (once the end is within 10 Tefachim, he turns it on the writing).

(R. Yosi citing R. Yochanan): [the first Tana permits rolling back] not only a Sefer, rather, even a belt. (We explained this like GILYON HA'SHAS.)

(Mishnah): If a ledge is in front of a window, we may put things on it and take from it on Shabbos.

(Gemara): This is when there is only one [window that uses the ledge], but if there are two, it is forbidden, for two Reshus may not use one Reshus.

This is when [the ledge] is four [by four Tefachim] wide, but if it is not four wide [even two are permitted], this is like R. Acha taught in the name of R. Yochanan;

Ledges and walls that are 10 tall and not four wide, [they are Mekom Petur, and] they are permitted here (to Reshus ha'Yachid) and here (to Reshus ha'Rabim), as long as they do not transfer (from Reshus ha'Rabim to Reshus ha'Yachid via the Mekom Petur. We explained this like HAGAHOS R. DINAR, SEFER NIR, HA'GAON RAV C. KANIEVSKY, SHLITA.)