A folding door is a type of door

Door

A door is a movable structure used to open and close off an entrance, typically consisting of a panel that swings on hinges or that slides or rotates inside of a space....

 which opens by folding back in sections. They are usually to be found indoors. Folding doors were already known by the Romans

Ancient Rome

Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

 as excavations in Pompeii

Pompeii

The city of Pompeii is a partially buried Roman town-city near modern Naples in the Italian region of Campania, in the territory of the comune of Pompei. Along with Herculaneum, Pompeii was destroyed and completely buried during a long catastrophic eruption of the volcano Mount Vesuvius spanning...

have revealed.

Folding doors may also known as accordion door or accordion partitions. Folding doors are designed to provide quick and easy space division with moderate sound attenuation and a pleasing visual appearance. Accordion doors and partitions provide quick sight and sound division with a simple pull-and-latch operation. Accordion doors and partitions are available as single and paired openings. For optimal design flexibility, curved track allows the partition to move around corners.