אורח חיים שצ״בOrach Chayim 392

Se’if 1א׳

עִיר שֶׁהָיְתָה קִנְיַן יָחִיד, אֲפִלּוּ נַעֲשֵׂית שֶׁל רַבִּים, מִשְׁתַּתְּפִים כֻּלָּם שִׁתּוּף אֶחָד וִיטַלְטְלוּ בְּכָל הַמְּדִינָה. וְכֵן אִם הָיְתָה שֶׁל רַבִּים וְיֵשׁ לָהּ פֶּתַח אֶחָד, מִשְׁתַּתְּפִים כֻּלָּם שִׁתּוּף אֶחָד. אֲבָל אִם הָיְתָה שֶׁל רַבִּים, וְיֵשׁ לָהּ שְׁנֵי פְּתָחִים שֶׁהָעָם נִכְנָסִים בָּזֶה וְיוֹצְאִים בָּזֶה, אֲפִלּוּ נַעֲשֵׂית שֶׁל יָחִיד אֵין מְעָרְבִין אֶת כֻּלָּהּ, אֶלָּא מַנִּיחִין מִמֶּנָּה מָקוֹם אֶחָד, אֲפִלּוּ חָצֵר אַחַת וּבַיִת לְתוֹכָהּ, וּמִשְׁתַּתְּפִין הַשְּׁאָר וְיִהְיוּ אֵלּוּ הַמִּשְׁתַּתְּפִין כֻּלָּם מֻתָּרִים בְּכָל הָעִיר חוּץ מֵאוֹתוֹ מָקוֹם שֶׁשִּׁיְּרוּ, וְיִהְיוּ אוֹתָם הַנִּשְׁאָרִים מֻתָּרִים בִּמְקוֹמָם בַּשִּׁתּוּף שֶׁעוֹשִׂים לְעַצְמָם. וְאִם הָיוּ הַנִּשְׁאָרִים רַבִּים, אֲסוּרִים לְטַלְטֵל בִּשְׁאָר כָּל הָעִיר. וְדָבָר זֶה מִשּׁוּם הֶכֵּר הוּא, כְּדֵי שֶׁיֵּדְעוּ שֶׁהָעֵרוּב הִתִּיר לָהֶם לְטַלְטֵל בְּעִיר זֶה שֶׁרַבִּים בּוֹקְעִים בָּהּ שֶׁהֲרֵי הַמָּקוֹם שֶׁנִּשְׁאַר וְלֹא נִשְׁתַּתֵּף עִמָּהֶם אֵין מְטַלְטְלִים בּוֹ אֶלָּא אֵלּוּ לְעַצְמָן וְאֵלּוּ לְעַצְמָן. וְאִם רָצוּ לְעָרֵב מָבוֹי מָבוֹי בִּפְנֵי עַצְמוֹ, כָּל שֶׁכֵּן דְּמַהֲנֵי דְּאֵין שִׁיּוּר גָּדוֹל מִזֶּה. הַגָּה: וְצָרִיךְ שֶׁיַּעֲשׂוּ בֵּינֵיהֶם שְׁנֵי פַּסִּין שֶׁל שְׁנֵי מַשְׁהוּיִין אִם הוּא רָחָב עֶשֶׂר (אַמּוֹת), וּבְיֶתֶר מִי' צָרִיךְ צוּרַת פֶּתַח. (טוּר).

Laws of City Eruvin. Containing 8 paragraphs: A city that has been the property of an individual, even if it became public- everyone can join in one partnership, and carry throughout the whole estate. Similarly, if it is publicly owned and it has one entrance- everyone can join in one partnership. But if it is publicly owned and and has two entrances, where the populace goes in one and out the other, even if the area came under private ownership, we may not make the whole thing into an Eruv. Rather, we must exclude a place, even as small as one courtyard and the house within it, from the city, and join the rest of the city together. Then all the participants in the partnership will be permitted in the whole city, except that one place that they excluded, and those residents remaining will be permitted in their own location, through a partnership they make for themselves. But if there are many residents remaining, it is forbidden to carry in the entire city. This is a provision instituted for the purpose of recognition, so that the residents will be aware that the Eruv has permitted them to carry in this place. The public becomes become expert on it, observing that we do not carry in the place that was excluded and not joined with them, but rather these carry in their own space and those carry in their own space. If residents wanted to institute an Eruv for each alley on its own, that would certainly be effective, for there is no greater exclusion than this.

Se’if 2ב׳

עִיר שֶׁל רַבִּים שֶׁיֵּשׁ לוֹ פֶּתַח אֶחָד וְסֻלָּם בְּמָקוֹם אַחֵר, מְעָרְבִין אֶת כֻּלָּהּ וְאֵינָהּ צְרִיכָה שִׁיּוּר, שֶׁאֵין הַסֻלָּם שֶׁבַּחוֹמָה חָשׁוּב כְּפֶתַח. וַאֲפִלּוּ הֶעֱמִיד הַרְבֵּה סֻלָּמוֹת זֶה בְּצַד זֶה עַד רֹחַב עֶשֶׂר, לֹא חָשִׁיב כְּפֶתַח. וְאִם יֵשׁ לָהּ שְׁנֵי פְּתָחִים וְיֵשׁ אַשְׁפָּה לִפְנֵי אֶחָד מֵהֶם, כְּאִלּוּ אֵין שָׁם אֶלָּא פֶּתַח אֶחָד.

A city of many people that has a first entrance and a ladder in another place, they are all mixed up and it is not necessary to remember that the ladder in the wall is not considered as a door, and even if many ladders are placed side by side up to a width of ten, it is not considered as a door. And if it has two doors and there is a garbage pile in front of one of them, it is as if there is only a first door there:

Se’if 3ג׳

הַבָּתִּים שֶׁמַּנִּיחִים אוֹתָם שִׁיּוּר, אַף עַל פִּי שֶׁאֵינָם פְּתוּחִים לָעִיר אֶלָּא אֲחוֹרֵיהֶם לָעִיר וּפְנֵיהֶם לַחוּץ, וַאֲפִלּוּ הוּא רַק בַּיִת אֶחָד אֲפִלּוּ בֵּית הַבָּקָר אוֹ בֵּית הַתֶּבֶן שֶׁאֵינָם צְרִיכִים לְעָרֵב, עוֹשִׂים אוֹתָם שִׁיּוּר וּמְעָרְבִין אֶת הַשְּׁאָר.

The houses that are placed separately, even though they are not open to the city, but have their backs to the city and their faces are outside, and even if it is (just one house, even) a cattle house or a hay house that does not need to be fenced, they are considered separate, and the rest of the houses are fenced: