A portcullis is a heavy grilled door or gate that can be dropped or raised to secure the entrance of a castle or fortified building. Typically made of wood or iron, it is designed to protect against intruders and can be quickly lowered in times of attack. The portcullis is often found at the main entrance, working in conjunction with other defensive features like walls and moats. In medieval times, the portcullis was an essential part of castle defense, often used alongside drawbridges and battlements. Its design allowed for quick access control, making it difficult for enemies to breach the stronghold. The mechanism for operating a portcullis usually involved a system of ropes and pulleys, allowing defenders to respond swiftly to threats.