How the Requirements of a City Eruv Work Together
No single feature establishes a city eruv. The enclosure must be suitable for the domains it surrounds, and the communal and supervisory requirements must then be added.
The status of the area comes first
Before selecting wires or walls, the responsible Rav must determine what kind of domains are being enclosed. A karmelis can often be enclosed with tzuras hapesach, while a Torah-level reshus harabim may require actual doors or another stronger solution.
Only after that psak can the physical route be designed. The form of the enclosure depends on the status of the streets it is meant to surround.
The communal arrangements follow the enclosure
Once a valid boundary exists, eruv chatzeiros or shitufei mevo'os joins the residents, and sechiras reshus is arranged where required. These steps address rights and rabbinic restrictions within the enclosed area.
They cannot be used in reverse to validate the boundary. Shared food makes separate residents one for carrying; it does not create a wall.
Inspection preserves an accepted system
The route then needs a precise record, trained inspection, competent repair, and a way to notify the public when carrying is not permitted. Inspection checks whether the structures accepted by the psak remain in place.
It does not decide the original halachic design from week to week. That responsibility stays with the Rabbonim who authorized the eruv.
One missing part affects the whole
Weekly inspection cannot cure a reshus harabim problem, shared food cannot close a breach, and a strong wall on one side cannot repair an open side elsewhere.
The word eruv often refers to the whole arrangement. In practice it is a chain of distinct requirements, and public permission depends on all of them working together.