If one [resident] of the outer forgot to contribute to the eruv, the inner is permitted while the outer is prohibited. If one from the inner [forgot], both are prohibited. If they placed their eruv in one place, and one [resident] of either the inner or the outer forgot to contribute to the eruv, both are prohibited. But if they were inhabited by individuals, they need not make an eruv.

A window between two courtyards — [if it is] four by four [fists] within ten, they may make two eruvin, or, if they wish, they may make one eruv; less than four by four or higher than ten, they may make two eruvin, but may not make one eruv.