What portable structure did Leonardo da Vinci design to span a gap without permanent supports?

Leonardo da Vinci designed a self-supporting bridge that could span a gap without permanent supports.

The bridge used interlocking timber elements arranged so that the pieces supported one another. This made it possible to assemble a crossing quickly and take it apart after use, an advantage for military movement.

Leonardo’s design is often described as a portable or emergency bridge. It did not depend on nails, ropes, or fixed piers in the way many conventional bridges did. The geometry allowed the weight of the timbers to help lock the structure together.

The bridge is frequently discussed as an example of Leonardo’s practical engineering. Modern demonstrations have built versions from logs or beams, showing that the basic principle works. It should not be confused with Leonardo’s other bridge proposals, including a large single-span bridge associated with Constantinople.