FORTIFICATIONS AND WAR MACHINES

— A type of ravelin: a wedge-shaped, triangular fortification placed outside the main ditch of a fortress for a fortress¹.

— Foundation for crenellations: the notched battlements atop a wall, providing gaps for soldiers to fire through.

— This system is for placing the underside of beam p into the top of beam q. Leonardo is likely describing a specific type of timber joint or interlocking mechanism for the structural framework of a fortification or siege machine.

— This is a type of square tower, shown as it would appear in a top-down plan, upon which the battlements are constructed.

— Cat: a "gatto," or a movable protective gallery used by besieging armies to safely approach a wall or fill a moat. — Foundation of a "cat" at m distance from the wall; this one will be damaged neither from above nor from below, nor from the side. Leonardo’s design emphasizes total protection for the soldiers inside, ensuring the machine is impervious to projectiles or undermining.

1. Venturi, Essay on the physical works of Leonardo da Vinci, p. 25, fig. 12.