Given that my two children are mere toddlers, I’m not worried yet about the last-fort problem. I’m still working on figuring out how to build a half-decent one, what with my severe deficit in engineering skills. I’m expert in the field of collapse. So I reached out to Ms. Foster and other architectural experts for help with constructing the perfect pillow-and-blanket structure.

But my search for practical counsel unearthed something else, too. I discovered some tears, an enthusiasm I didn’t quite anticipate and, in the end, something unexpected. I won’t look at a pillow fort in quite the same way again.

The Seattle architect and blogger Andrew van Leeuwen stumbled upon the emotional resonance of forts when he wrote a lighthearted posting about them several years ago. Traffic soared.

“It overwhelmed the server, and we had to shut the post down,” he said, laughing.

Memories of my earliest forts are hard to conjure up. I do remember the feelings, though: huddled in a cave made of cushions and sheets with my younger sister, we conspired to figure out how to create windows and doors in our private space. We often brought in a guest — our cat, Frisky — but the scratch marks on our forearms attested to her interest in being excluded.

I’ve also talked to lots of friends and acquaintances about forts, and heard the same warm feelings about an almost universal childhood activity, one often shared with parents. Cost: zero. Rules: few. Comfort of a cave: high. Cleanup: well, there’s that.