One who was to the east and had told his son, ‘‘Make an eruv for me in the west’’; to the west and had told his son, ‘‘Make an eruv for me in the east’’ — if the distance from him to his house is two thousand cubits and to his eruv more than that, he is permitted [the techum of] his house but forbidden [the techum of] his eruv; if to his eruv is two thousand cubits and to his house more than that, he is forbidden [the techum of] his house but permitted [the techum of] his eruv. One who places his eruv in the extension of a town has accomplished nothing. If he placed it beyond the techum, even one cubit, whatever he gains he loses.