A trap door is a hinged or removable panel in a floor, ceiling, or wall that provides access to a hidden space. Often used in buildings, theaters, and even in some vehicles, trap doors can serve various purposes, such as storage, secret passages, or emergency exits. They are designed to blend in with the surrounding structure, making them discreet and sometimes surprising when opened. In historical contexts, trap doors have been associated with secret rooms or escape routes in castles and theaters. They can also be found in modern applications, such as in stage productions where they allow for special effects or quick scene changes.