Responsa על עירובין 143:12

Q. The occupants of an alley performed the ceremony of shittuf-mabo [association of courtyards which open into a common alley by placing a cross-beam over the alley-entrance, and placing food belonging to the occupants of the alley in one court-yard, thus transforming the different court-yards and the alley into one single domain, held jointly by the occupants, in the limits of which it is permitted to carry objects on the Sabbath]. If the cross-beam over the alley-entrance broke down, are the occupants permitted to carry objects on the Sabbath within the limits of their respective court-yards, and from one court-yard to the next one?
A. All the court-yards from which one can enter, directly or through other courtyards, into the one where the common-food has been deposited, without having to cross the alley, form a single domain within the limits of which, objects may be carried on the Sabbath. In the remaining court-yards, one is not permitted to do so.
SOURCES: Cr. 39; Pr. 422; Mord. Erub. 518; Hag. Maim. to Erubin 3, 6.

If the occupants of court-yards which open into a common alley-way, have associated their court-yards through the ceremony of shittuf (cf. M. Erub. 7, 6), the courtyards, together with the alley-way, become a single domain within which objects may be carried on the Sabbath. Such a ceremony renders unnecessary any further association of the different premises within each court-yard through the ceremony of Erub.
SOURCES: Pr. 89; cf. Hag. Maim., Erubin 1, 9.

Q. The occupants of an alley performed the ceremony of shittuf-mabo [association of courtyards which open into a common alley by placing a cross-beam over the alley-entrance, and placing food belonging to the occupants of the alley in one court-yard, thus transforming the different court-yards and the alley into one single domain, held jointly by the occupants, in the limits of which it is permitted to carry objects on the Sabbath]. If the cross-beam over the alley-entrance broke down, are the occupants permitted to carry objects on the Sabbath within the limits of their respective court-yards, and from one court-yard to the next one?
A. All the court-yards from which one can enter, directly or through other courtyards, into the one where the common-food has been deposited, without having to cross the alley, form a single domain within the limits of which, objects may be carried on the Sabbath. In the remaining court-yards, one is not permitted to do so.
SOURCES: Cr. 39; Pr. 422; Mord. Erub. 518; Hag. Maim. to Erubin 3, 6.