A portcullis is a heavy grilled door that can be dropped down to secure the entrance of a castle or fortified building. Typically made of wood or iron, it is designed to protect against intruders. When raised, it allows entry, but when lowered, it acts as a strong barrier. Portcullises were often used in conjunction with other defensive features, such as moats and drawbridges. They could be quickly deployed in times of attack, providing an effective means of defense. This mechanism was common in medieval architecture, particularly in European castles.