910. Eiruv and Shittuf

Eiruvin 1:7

When the residents of a courtyard make an eiruv among themselves, it is called “eiruvei chatzeiros” – the combining of courtyards. When residents of a common alley or a city make an analogous arrangement, it is called shittuf – a partnership.

Eiruvin 1:8

An eiruv for a courtyard may only be made using a whole loaf of bread. A large, sliced loaf is unacceptable while a small, whole loaf is fine. This loaf may be made from grain, rice or lentils but not from millet. A shittuf, however, made be made using bread or other types of foods except for water and salt. Mushrooms and truffles may likewise not be used for a shittuf because they are not considered foods. Water and salt are only excluded when put aside in their own rights; water and salt mixed together is considered brine and may be used for a shittuf.