A merlon is a solid part of a battlement, which is a defensive structure found on the walls of castles and fortifications. It is the raised section that alternates with the openings called crenels, allowing defenders to shield themselves while shooting arrows or other projectiles at attackers. Merlons are typically rectangular or square in shape and provide both protection and a vantage point. Historically, merlons were an essential feature in medieval architecture, contributing to the overall strength and functionality of a castle. They are often seen in conjunction with other elements of fortification design, such as parapets and towers, which together helped defend against sieges and invasions.