“See, this wire connects to that telephone pole,” says Rabbi Shlomo Zarchi of Congregation Chevra Thilim, gesturing as he stands on the corner of 16th Avenue and Clement Street in San Francisco. “And then it jumps to that one over there. Can you see it?”

To the untrained eye, it might not look like much: some wire stretched between telephone poles, an extra bit of wood here and there. But to shomer Shabbat families in San Francisco’s Richmond District, the establishment of an eruv last November signified that this was now a place where young, observant couples could raise their families.

Who says there’s no Jewish neighborhood in San Francisco?

In its simplest terms, an eruv (Hebrew for “mixed together”) is an enclosure that allows observant Jews to carry objects from a private domain (such as one’s home) to a public domain (a shul, a neighbor’s house for dinner) on Shabbat — behaviors that, according to halachah, or Jewish law, are otherwise forbidden. This is especially important to Shabbat-observant Jews, because it permits parents to carry their infants from place to place, and allows people to tote objects like a tallit bag or a platter of cookies.

According to those who rely on an eruv, its importance — both in facilitating the practicalities of day-to-day life for those who already live in the neighborhood, and its potential to strengthen a community and attract new Jewish residents — can’t be overestimated.

“We’ve grown close to other young couples here, and the eruv is definitely part of that,” says Jeremy Hollander, 31, who moved to the Richmond District with his wife, Susan, just as the eruv was being built last year; their daughter, Ilana, was born in September. When the expectant couple decided to move from Miami to the Bay Area for Hollander’s work, they started by looking for Jewish neighborhoods.

“I wanted to make sure there was a vibrant community for us: young people, a place where we could bring the baby to shul, walk around on Shabbat. That’s a big part of our lives,” says Hollander, who belongs to Chevra Thilim, the Modern Orthodox congregation on 25th Avenue between Balboa and Cabrillo streets that was instrumental in getting the eruv built. “It makes such a difference — things like just being able to go over to someone’s house for Shabbat dinner. It’s a good time to be here.”

The Richmond District eruv, which officially launched on Nov. 23, 2012, is the Bay Area’s fourth. It runs east to west between 16th and 43rd avenues, and north to south from Clement Street to Golden Gate Park.

In San Francisco, there is also a Sunset District eruv, affiliated with Congregation Adath Israel, which is marking its fourth anniversary this summer.

“Except for city officials and [observant Jews who use it], no one really knows it’s here,” says Rabbi Joel Landau of Adath Israel, a Modern Orthodox synagogue on Noriega Street at 26th Avenue. “But for the people who do use it, it’s very clear that it’s a major factor in determining the desirability of a place to live.” A celebration of the eruv’s anniversary is in the works for later this month, the rabbi says.

In Palo Alto, the eruv enclosing Stanford University and much of the surrounding area was established in 2007 after an eight-year battle with the city. In the East Bay, the Berkeley eruv, established in 2004, covers parts of downtown, West Berkeley, North Berkeley and Albany.

The boundaries of an eruv — which can employ wire, fabric and wood as well as existing natural or man-made resources such as trees, fences or houses to form “gates” — can encompass just a few blocks around a synagogue, or an entire neighborhood or city. The walls around ancient Jerusalem were the first eruv, Zarchi notes.

On a recent Friday morning, Zarchi was out checking the Richmond eruv, a weekly duty to inspect the boundary to make sure it hasn’t been damaged. If all is well, the word goes out that the eruv is “up.” If even a small part is damaged, the eruv is “down,” and observant Jews can’t carry anything outside their homes during that Shabbat. In a twist on a centuries-old concept, this eruv, like many, employs a Twitter account (@sferuv) to let followers know when the eruv is “up.”

Pointing out boundary markers that are sometimes barely visible, Zarchi says his goal is to expand the eruv south so it crosses Golden Gate Park, and east so it encompasses Congregation Beth Sholom, a Conservative synagogue whose clergy and members Zarchi has been working with, and Congregation Emanu-El, a Reform synagogue near Second Avenue.

At one point, Zarchi spent several hours on a boat just off Fisherman’s Wharf with a full-time eruv consultant he brought in from Miami, trying to figure out if it would be possible to enclose all of San Francisco within an eruv; under certain guidelines, a seawall can serve as a boundary.

But for now, Zarchi is pleased with what he and the eruv’s other planners — he gives much credit to Adath Israel’s former rabbi, Rabbi Joshua Strulowitz, for his work with San Francisco officials — have been able to accomplish.

“Being a rabbi in a city like San Francisco, it’s my job to help people engage more deeply with Judaism, to bring more people into the fold of Jewish life and observance,” Zarchi says. “And for some [Orthodox] people, the eruv is going to be the difference between their coming to synagogue or not. Shabbat is not supposed to be a triathlon. It’s hard enough as it is.”

Parents with young children who live outside an eruv — such as the Orthodox community near Beth Jacob Congregation in Oakland, which as of yet has no eruv — sometimes hire non-Jewish stroller pushers to help get their families to shul. But for many others, the solution is often one parent simply staying home.

Avoiding having to make that kind of choice was one big motivator for Rachel Toaff-Rosenstein, 31, who relocated to California from Philadelphia with her husband, Arye, and then-6-month-old twins in 2010. After looking into Orthodox communities in different parts of the Bay Area, they settled on living within the Berkeley eruv.

In addition to their now 3-year-old kids, the couple has a 4-month-old infant, making the eruv “essential for us,” she says.

“I love pushing my kids in the stroller, and to be honest I would feel kind of awkward paying someone else to do that,” she says. “And being inside the eruv is kind of instant community. We didn’t have any family or friends when we moved here, and it’s really helped with acclimating. My husband is one of the [eruv] checkers before Shabbat, and it’s nice to feel like he’s giving back to the community in that way.”

It also helps to have dozens of other young parents on hand at a moment’s notice, says Toaff-Rosenstein, who estimates that at least “17 or 18 babies have been born in the last 12 months” at Congregation Beth Israel, which is within the eruv’s boundaries. “It’s a support system,” she says. “Especially when you have a newborn, feeling like you have other moms to talk to is wonderful. And being able to see each other on Shabbat makes a real difference.”

Jonathan Esensten and Raquel Gardner, a couple now living within the boundaries of the Sunset eruv, echo that statement. They had lived in a few different neighborhoods in San Francisco over the past five years, but, with starting a family in mind, they moved inside the eruv in early 2010, about six months after it was completed. They now have a 2-year-old son and an infant daughter.

“Shabbat can be pretty lonely if you’re home with a couple of kids,” says Esensten, 33. “And it’s not just for going to synagogue: You can go to the playground. We can go from home to home. We know a lot of our neighbors. It really brings people together to have that in a neighborhood — something I think was more common at different times and places in the world. That’s a powerful thing.”

In Palo Alto, the Orthodox community finally established an eruv in 2007 after eight years of public debate about whether it would violate federal regulations concerning the separation of church and state. The battle involved heated city council meetings and scathing letters to the editor in the local papers, with those against the eruv claiming that it would be a city-funded religious symbol, in violation of the Constitution. Then–City Attorney Gary Baum eventually ruled that it was permissible.

Since that rocky start, there have been “no important issues in the last six years,” says Rabbi Yitzchok Feldman of Congregation Emek Beracha in Palo Alto. On the contrary, he adds, there has been “great cooperation from the Palo Alto police whenever a fix is needed.

“[The eruv] is the No. 1 reason why couples who want to have families come here,” says Feldman, referring to several baby “boomlets” since the eruv went up — in one year, 25 babies were born to members of the congregation; another year, 15.

“Observant young couples come to Palo Alto, despite the prohibitive price of housing here, because an eruv is an essential part of Jewish infrastructure,” he says. “When folks call from elsewhere — from Israel or from more established communities in the U.S. — they’re looking for the staples of modern Orthodox life. They want to know about a school, a mikvah and an eruv. Now we have all three in the area.”

None of the other Bay Area eruvs faced quite the level of public scrutiny Palo Alto’s did. But many people involved in their planning mentioned that they purposefully did the bulk of the actual work at night, including taking measurements and, in the case of the Richmond eruv, attaching extra bits of wood to telephone poles and wires.

“In the last couple of weeks before we went live, we had maybe five to 10 people working on it at night, just to minimize interference, to minimize a scene that would cause people to notice,” Zarchi says.

One row of houses on 43rd Avenue actually serves as part of the boundary; its residents likely don’t know that their homes are serving a Jewish ritual function, “but there’s no need for them to,” Zarchi says.

One person who did take notice of the nighttime excursions up telephone poles in San Francisco was an elderly woman who apparently repeatedly called Comcast to report people stealing her cable in the nighttime, the rabbi says with a laugh.

“I had actually just finished driving around with a PG&E representative, to show him everything when it was finished so that he could feel OK about there being no safety hazards, and we’re sitting in the car when this elderly lady comes over and says ‘Are you an official from PG&E? I have a complaint!’ ” Zarchi recalls.

“She says, ‘The other night we saw a bunch of suspicious people pirating channels …’ and she’s talking to this guy for a good seven or eight minutes before she looks at me and kind of turns white and goes ‘You’re one of them!’ I spent a long time with her explaining what it was, who I was, how this is unifying our community. By the end she seemed to get it, but she was still pretty suspicious.”

Eruv do’s and don’ts

What you can and can’t carry inside an eruv on Shabbat:

CAN

Tallit bag

Prayerbook

House keys

Clothing that has been removed

on warm days

Reading glasses

Baby in a carriage or stroller

(equipped with food and diapers)

Bottle of wine

CAN’T

Umbrella

Pens

Items that will be used only after Shabbat, such as something for

a Saturday night party

Money

Car keys

Cellphone

Golf clubs

Sources: Chabad.org and MyJewishLearning.org