The Ingenious Engineering of Leonardo da Vinci's Self-Supporting Bridge, Explained
Briefly

The key is the distinctive manner in which the pieces interlock, and how it directs force to create a 'friction lock' that ensures stability. Removing just one piece, however, leads to collapse; this feature is intentional, allowing for rapid dismantling to hinder enemy use.
Leonardo's bridge designs have proven influential over the half-millennium since his death. Although no evidence remains that he built one in his lifetime, one can construct it today with ease.
Read at Open Culture
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