How was a portcullis used to defend?

A portcullis was a heavy grilled gate or barrier made of wood and iron, used in medieval castles and fortifications to enhance security. It could be dropped quickly to block entry during an attack, making it difficult for invaders to breach the entrance. The design allowed defenders to control access while providing a means to protect the gate from siege weapons. Additionally, the space above the portcullis often served as a defensive position for archers or other defenders.