My tiny apartment is doorbell-free. No surprise, really: Tenants in this building have few visitors. When any do come, they go directly to their target-door and bang on it. In my case, the only regular visitor is the mail-carrier, bringing parcels from Amazon. He knocks, leaves the parcel and goes away before I can say “thank you”.

This bothers me for two reasons. One, I like thanking mail-carriers because I honestly believe the postal services are the best feature of urban life. Two, I worry that regular banging will result in smudges on my plain white door. So. The other day, I decided to rig up a cottage-industry device, consisting of two simple little bells, supposedly used on goats and sheep, that I bought at the Crafts Museum gift shop in New Delhi.

They make a very sweet tinkling sound and they’re attached to key-chains. I bought them for this very purpose. I tied one bell to either end of a long sturdy cord. I suspended the cord from a hook just above my door in such a way that if one end of the cord is pulled, both bells tinkle. When I’m at home, I allow one of the bells to dangle outside my door. Whenever I go out, I flip the cord over the top of the door, so that the bell dangles inside and cannot be rung.

Now here’s the problem: despite the fact that there’s no other ornament on my door, NO ONE RINGS THE BELL!! Today, I actually caught the mail-carrier in the act of vanishing after knocking on my door. When I said, “Hi! Thanks for the delivery! Umm... may I make a request? Please could you ring this bell?” Whereupon, the nice young man chuckled out loud and said, “What? Oh! Sorry — didn’t see it! That’s really cute!” And left.

This is an excellent example of something that’s in plain view but functionally invisible. A book I’m reading focuses on something similar, in connection with cities. It’s called The 99% Invisible City by Roman Mars and Kurt Kohlstedt, about the vast unseen networks of design and engineering that surround a city dweller. There’s a shadow-language of words, symbols and signs that most of us never notice unless they’re pointed out to us.

For instance, I’ve often seen bright chalk marks on the sidewalks and road surfaces here. Pink, orange, white and yellow scribbles. I never knew what they meant, but it turns out they provide civic engineers with crucial information about gas lines, sewage pipes, buried electrical cables and so on.

There’s so much interesting trivia in this book that I’ll have to share it in my next column! I’ll end with three words that are new to me: Vexillology, the study of flags. Synanthropes, formerly wild creatures such as raccoons, who have adapted to living alongside humans. And Thomassons, vestiges of once-useful architecture, kept on as ornaments, such as a flight of stairs leading nowhere.

Manjula Padmanabhan, author and artist, writes of her life in the fictional town of Elsewhere, US, in this weekly column

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