When the squares or rectangles formed around two cities overlap, even when there is no joint eruv, the overlapping area connects the cities. We draw a new rectangle around the entire area to include both cities. The residents of both cities may then walk 2,000 amot beyond the joint rectangle.
However, if the distance separating the corners of the two rectangles is greater than 4,000 amot, as we have seen (section 7), we do not square the entire area. Rather, each city is assigned a standard teĥum of 2,000 amot beyond its rectangle in each direction.