An arrow slit is a narrow vertical opening in a wall, typically found in medieval castles and fortifications. These slits allowed archers to shoot arrows at attackers while providing protection from incoming projectiles. The design of arrow slits maximized visibility and minimized exposure, making them effective defensive features. Arrow slits are often associated with medieval architecture and were commonly used in fortresses and castles throughout Europe. They are a key element of military engineering from the Middle Ages, showcasing the importance of defensive strategies in protecting against sieges and invasions.