[Image courtesy of Letter Writers Alliance.]

When you think about puzzles and personal security, what comes to mind?

Do you think of puzzle boxes, those delightfully tricky little wooden creations with all their sliding pieces and hidden compartments? Or does your mind go to encryption, the art of concealing your message in plain sight with ciphers, scytales, and other techniques meant to baffle anyone but those in the know?

Some puzzle box designs date back centuries, and ciphers can be traced back even further. (One is named after Caesar, after all.)

But there’s another centuries-old puzzly procedure you might not know about, and it kept letters and messages safe using nothing more than paper and wax.

[Image courtesy of ibookbinding.com.]

This technique is known as letterlocking. It involves a mix of precise folds, interlocking pieces of paper, and sealing wax in order to create a distinctive design or pattern.

Although the pattern itself can work like a puzzle — requiring a particular trick to unfold it and reveal the message without ripping or damaging the letter — that’s only a secondary line of defense. The true goal of letterlocking is to reveal tampering. The folding techniques are distinctive, and the wax creates points of adhesion.

If you receive a letter and the folds are done (aka redone) incorrectly, or the wax is smeared (or the paper ripped where the wax would have held it tight), then you know the letter has been compromised.

[Image courtesy of ibookbinding.com.]

Some examples of letterlocking trace back to the 13th century, and key figures like Queen Elizabeth I, Machiavelli, Galileo, and Marie Antoinette employed letterlocking security in the past. Mary, Queen of Scots, wrote a message and letterlocked it with a butterfly lock six hours before her beheading. (For a more modern reference, letterlocking was employed in the Harry Potter films as well, most famously in Dumbledore’s will.)

The various techniques involved are as distinctive as knots. The triangle lock. The dagger-trap. The pinwheel letter. And some historians believe that those techniques imply connections between some of the important players in history.

For instance, both poet John Donne and the spymaster of Queen Elizabeth I employed a similar letterlocking style. Did they share a common source, or even an instructor in common? Or did a particular letterlocking technique provide a clue as to the contents of the letter within?

Letterlocking is a historical curiosity that was seemingly lost to time after the proliferation of the envelope and other security techniques, but it is slowly being rediscovered by a new generation, as well as reverse engineered by scientists and scholars. Yale and MIT both have teams exploring the burgeoning field of letterlocking.

Museums are discovering treasure troves of letterlocked messages by going directly to the source: post offices. A cache of 600 undelivered letters in the Netherlands, for instance, are being analyzed by researchers.

[Image courtesy of Atlas Obscura.]

It’s a remarkable thing, really, this union of centuries-old skills with twenty-first century knowledge. These are puzzles, frozen in time, waiting to be solved and placed into the larger picture of history.

Letterlocking is nothing less than a rare and beautiful art combining puzzles and privacy, as elegant as it is clever. There are no doubt many more secrets to be found behind the folds, slits, and wax seals of these lovingly crafted messages.

Thanks for visiting PuzzleNation Blog today! Be sure to sign up for our newsletter to stay up-to-date on everything PuzzleNation!

You can also share your pictures with us on Instagram, friend us on Facebook, check us out on Twitter, Pinterest, and Tumblr, and explore the always-expanding library of PuzzleNation apps and games on our website!