Portable bridges to flee or pursue the enemy
Bridges of lashed poles on forked trestles, raised with a jack and hooked together
Two studies show light bridges spanning a river, each built from long poles or tree-trunks lashed together and carried on forked, sawhorse-like trestles; a workman kneels at the left of the upper bridge. Leonardo describes these framings as bridges to be set up quickly, fit for fleeing or pursuing the enemy: the projecting ends of the timbers, bent down toward the water by their own weight, are lifted with a jack (martinetto) and tied, and further forked supports are added one after another. Hooks set every six braccia let the members be opened and woven together like a braid. The sheet also carries faint sketches and figures — the Ambrosiana index notes crossbows, bombards, a remark on inertia and readings of large numbers or expense notes — that are not part of the transcription.
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Framings for a bridge to flee or pursue the enemy
The heading treats the structures as 'framings' and asks how one should set up a bridge quickly. Their stated purpose is military: bridges fit for fleeing from or pursuing the enemy.
Raising the bent timber-ends with a jack
Once the timbers are fixed on the forked support and their tips project into the air, their weight bends them toward the water. Leonardo directs that they be raised again with the jack, tied, and then a further fork set behind, proceeding step by step; the ends held up in the air must be raised high enough to take their support.
Hooks every six braccia, woven like a braid
The bridge is called very convenient and quick, with hooks placed every six braccia as drawn in front. If these hooks are opened at their ends, the members can be woven together like a braid.