אסרו חכמים לטלטל מן החצירו' למבוי והתירוהו ע"י שיתוף שגובין פת או דבר אחר ממיני מאכל מכל חצר וחצר ונותנים אותו בא' מן החצירו' ואנו רואים כאלו פתוח כל המבוי לאותו חצר ומפני שאינו אלא לשתף החצירו' יכולים ליתנו באויר החצר או בבית שאין לו ארבע על ארבע וא"צ ליתנו בבית רק שיהי' במקום המשתמר הילכך אין נותנין אותו באויר המבוי (וע"ל סי' שס"ו):

Laws of partnership in an eruv. Containing 9 paragraphs The Sages forbade carrying from courtyards into an alleyway, and permitted it through a partnership whereby bread or any other food is collected from each courtyard and placed in one of the courtyards, and we consider it as if the entire alleyway opens into that courtyard. Since this is only to create partnership among the courtyards, it may be placed in the airspace of the courtyard or in a house that is not four by four handbreadths, and need not be placed in a house — only in a protected place. Therefore it may not be placed in the airspace of the alleyway.

Jews living in three separate locations whose gates are each locked at night, and a beadle who collects flour from all of them — this does not help them make a partnership, since an alleyway partnership must be placed in a courtyard within the alleyway, and since they are separate from one another and distant, their partnership is not one and their alleyways are not one. Rema: If they made an eruv in one place, the others who did not make an eruv do not restrict them, since they have no foot traffic over one another, as the entire city is not considered one alleyway even though they live within one surrounding wall.

All the laws of eruv for courtyards — its required amount, that a man's wife may make the eruv on his behalf, that one may make an eruv without someone's knowledge if their house opens only to one courtyard, that a minor may collect it, and that one person may acquire on behalf of all (and that if they were already partners they need not make an eruv) — all these laws apply equally to the partnership eruv. Rema: Even if one was already partnered with his neighbors in merchandise — one in wine and one in oil — they need not make a partnership eruv, provided it is in one vessel.

One may make a partnership eruv with any type of food, and even four or five types of food may combine to make up two meals' worth.

One may make a partnership eruv with any type of food except for berries that have hardened to seed, spices, dry beans, onion tops that have not grown a handbreadth in length, truffles and mushrooms, unripe dates, lentils, wheat and barley, vegetables that are half-cooked, water alone, or salt alone. But if water and salt are mixed together one may use them, and some say only when oil was added to them. Some say one may make an eruv with spices.

For anything normally used as a relish with bread, the required amount is enough to serve as relish for bread eaten at two meals. For anything not used as a relish, the required amount is enough to eat at two meals. Raw meat is not considered a relish and requires enough to eat at two meals. Roasted meat is considered a relish and requires enough to serve as relish for two meals. Vinegar is considered a relish, as is cooked wine, but uncooked wine is not considered a relish and its required amount is two reviit, and similarly for other liquids.

One may make a partnership eruv with two eggs even raw, with two pomegranates, with five peaches, with a litra of vegetables whether raw or cooked, with a handful of fresh beans, or with a kav of forest apples.

One may make a partnership eruv even with food that is not suitable for him, if it is suitable for some person — such as wine for a nazirite or terumah for a Jew. Similarly, one who vowed or swore not to eat something may still make a partnership eruv with it. Some say this applies only when he vowed or swore not to eat it, but if he vowed or swore not to benefit from it, one may not make a partnership eruv with it for him. (And if he said konام on benefiting from it or eating it — according to all opinions one may not make a partnership eruv with it.) (Tur)

If one said of a loaf "today it is unconsecrated and tomorrow it is consecrated" or "konام" — one may make a partnership eruv with it, since during twilight it had not yet certainly become consecrated and it was suitable while it was still day. But if one said "today it is konام and tomorrow it is unconsecrated" — one may not make a partnership eruv with it since it is not suitable until nightfall. A courtyard opening into two alleyways that made a partnership with each of them — it is permitted to carry between it and each of them, but it is forbidden to carry vessels that rested in one alleyway to the other alleyway through the courtyard. If it made no partnership with either of them: if it regularly uses both by entering and exiting through them on weekdays, it restricts both. If it regularly uses one and not the other, the one it regularly uses restricts while the one it does not regularly use does not restrict. If it made a partnership with the one it does not regularly use, the one it regularly uses becomes permitted on its own if they made a partnership among themselves. Similarly, if it regularly uses both and made a partnership with one of them, the other is permitted since it removed itself from it. If the alleyway it regularly uses made a partnership among themselves and the one it does not regularly use did not make a partnership, and it made no partnership with either — we push it toward the one it does not regularly use and it removes itself from the one it regularly uses so that the latter is permitted, since it loses nothing by this as it made no partnership with them, and others gain from it — we compel it on account of the trait of Sodom.