Letterlocking: The Hidden History of the Letter

The rich history of a centuries-old document security technology—folding and securing a letter into its own envelope for delivery—and a comprehensive guide to learning how to make your own locked letters.

Before the invention of the gummed envelope in the 1830s, how did people secure their private letters? The answer is letterlocking—the ingenious process of securing a letter using a combination of folds, tucks, slits, or adhesives such as sealing wax, so that it becomes its own envelope. Th...