Building partitions between neighbors:[1]
Two people that are living in the same courtyard are required to build a wall in middle of the courtyard in order to separate it into two sections and prevent each other from seeing the actions and dealings of the other within the courtyard. [The neighbors are able to force each other to build a partition in the courtyard.[2]]
Building using charity money:[3] If they are poor and cannot afford to build a wall then if they are able to receive charity moneys in order to build a light partition between them, they are to do so.
If a partition is not built:[4] If they are not able to build a partition, the neighbors must beware as much as possible not to look at what the other person is doing in his property.
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[1] Admur Nizkei Mamon 11; Michaber 157/1; Mishneh Baba Basra 2a and Gemara 3a
[2] Michaber and Rama ibid; Gemara ibid
[3] Admur ibid; Smeh 157/11; Shach 157/6; Tur 157
[4] Admur ibid; Rama 157/3