All the roofs of a town are one domain, provided that one roof is not ten [fists] higher or lower [than the others] — [these are] the words of R’ Meir. But the Sages say: Each is a domain for itself. R’ Shimon says: Roofs, courtyards, and karpeifos are all one domain with respect to utensils which began the Sabbath in them, but not with respect to utensils which began the Sabbath in the house.

If a large roof is adjacent to a small one, the large one is permitted but the small one is prohibited. If a large courtyard was breached into a small one, the large one is permitted but the small one is prohibited, because it is like the entrance of the large one. If a courtyard was breached into a public domain, one who brings from there into a private domain, or from a private domain into it, is liable — [these are] the words of R’ Eliezer. But the Sages say: From it into the public domain, or from the public domain into it, is not liable, because it is like a karmelis.

If a courtyard was breached into a public domain on two of its sides, or if a house was breached on two of its sides, or an alley whose crossbeams or poles were re-moved; they are permitted on that Sabbath but prohibited in the future — [these are] the words of R’ Yehudah. R’ Yose says: If they are permitted on that Sabbath, they are permitted in the future; and if they are prohibited in the future, they are prohibited on that Sabbath.

A secondary story built upon two houses, or bridges under which a road passes, one may carry beneath them on the Sabbath — [these are] the words of R’ Yehudah. But the Sages prohibit. R’ Yehudah also said: We may make an eruv for an open alley. But the Sages prohibit.