Eruvin1: 8
שַׁיָּרָא שֶׁחָנְתָה בְּבִקְעָה וְהִקִּיפוּהָ בִּכְלֵי בְהֵמָה — מְטַלְטְלִין בְּתוֹכָהּ, וּבִלְבַד שֶׁיְּהֵא גָדֵר גָּבוֹהַּ עֲשָׂרָה טְפָחִים, וְלֹא יִהְיוּ פְרָצוֹת יְתֵרוֹת עַל הַבִּנְיָן. כָּל פִּרְצָה שֶׁהִיא כְעֶשֶׂר אַמּוֹת מֻתֶּרֶת, מִפְּנֵי שֶׁהִיא כְפֶתַח; יָתֵר מִכָּאן אָסוּר:
A caravan which made camp in a valley and surrounded it with animal trappings — they may carry within it provided that the barricade is ten fists high, and the gaps do not exceed the walled portion. Any gap which is ten cubits wide is permitted for it as an entrance; greater than this is prohibited.