There’s a Secret Wire high above New York that’s 18 miles long

Being Jewish in Manhattan comes with strings attached
High wire strewn through city lets Jews keep the faith
Orthodox Jews are allowed to push baby strollers and carry prayer books on the Jewish Sabbath thanks to a loophole made of fishing line that stretches some 18 miles on utility poles around the city.
The line forms a nearly invisible enclosure, called an eruv in ¬Hebrew. Jews are prohibited from doing these simple tasks outside on the Sabbath, but carry them out in the confines of the eruv because it symbolically turns a public space into a private one.
https://nypost.com/2015/05/24/high-wire-strewn-through-city-lets-jews-keep-the-faith/
https://www.hellalife.com/blog/people/wire-above-manhattan-eruv/