Slits of the height of a man and about a palm's width on the outside allowed defenders to shoot bows and scorpions (an ancient siege engine) from within the city walls. Although used in late Greek and Roman defences, arrowslits were not present in early Norman castles.

These narrow vertical openings are called arrowslits (or loops/loopholes). They were a revolutionary defensive feature in medieval military architecture designed to allow archers and crossbowmen to fire upon attackers while remaining almost entirely protected. A supportive peer "history" note: the genius of the design lies in the interior "embrasure." While the slit looks tiny from the outside, the wall on the inside is cut away at a wide angle, giving the archer a broad field of vision and room to move. In 2026, as you tour European castles, you'll notice different shapes: long vertical slits for longbows, and "cross" shapes that accommodated the horizontal limbs of a crossbow. These slits transformed stone walls into active "firing platforms" rather than just passive barriers.