What Leonardo da Vinci device was designed to make a bridge stronger with a triangular support?

Leonardo da Vinci designed a self-supporting bridge assembled from interlocking beams.

The design uses the weight and arrangement of its timbers to stabilize the structure without nails, ropes, or permanent supports. Beams cross and press against one another, producing a temporary bridge that can be assembled from separate pieces. Its geometry distributes loads through compression and friction.

This concept differs from Leonardo’s other bridge designs made for military transport. A folding or swinging bridge is defined by how it moves aside, whereas a self-supporting bridge is defined by how its parts lock together and carry weight. The two ideas are therefore related but not identical.

Modern demonstrations show that the structure can work when built accurately and loaded appropriately. Leonardo’s drawing illustrates his interest in modular construction: a bridge could be transported as components and assembled where needed.