The Ancient Art Of Self-Sealing Letters

Before envelopes were invented, people secured private letters by folding the paper into complex, interlocking patterns. These seals acted as a tamper-evident system that destroyed the paper if anyone tried to force it open.

This practice, known as letterlocking, dates back to the 13th century when paper became flexible enough to be manipulated. By creating intricate folds, slits, and tucks, writers ensured that any unauthorized access would leave permanent damage. It was the original high-security encryption for paper mail. Today, historians use digital scanning to unfold these fragile documents without breaking the original seals.