Crenelations served several purposes in medieval warfare. They allowed defenders to shoot arrows or pour hot liquids on attackers below without exposing themselves to enemy fire. They also helped to weaken the enemy's morale by making it appear that the castle or fortification was impregnable.
Crenelations were typically constructed of stone or brick, and they were often reinforced with iron or wooden beams. The spacing between the crenels varied, but it was typically around 1.8 meters (6 feet). The height of the crenels also varied, but they were typically around 1 meter (3 feet) tall.
Crenelations were a common feature of medieval fortifications throughout Europe, and they can still be seen in many castles and fortifications today.