What reusable bridge did Leonardo da Vinci design to assemble without nails, ropes, or mortar?

Leonardo da Vinci designed a self-supporting bridge that could be assembled without nails, ropes, or mortar.

The bridge uses interlocking wooden beams arranged so that their weight and geometry hold the structure together. Each beam supports neighboring pieces, creating a stable span through compression and friction. The design could be assembled from separate parts and taken apart again, making it useful in a temporary military context.

Leonardo’s sketch is usually dated to the late 15th century, when portable crossings were valuable for moving troops and supplies. The bridge demonstrates his ability to reason about structural forces even without modern engineering notation.

It is often confused with his revolving bridge. A self-supporting bridge stays in place through interlocking members, while a revolving bridge pivots to open a passage. Modern demonstrations have built replicas, but those are reconstructions based on Leonardo’s drawing rather than surviving original bridges.