A 'juǎn lián mén' (roller shutter door) is a type of security door made of interlocking horizontal slats—usually aluminum or steel—that roll up vertically into a compact coil above the doorway. The name breaks down literally: 'juǎn' means 'to roll', 'lián' means 'curtain', and 'mén' means 'door'—so it's a 'rolling curtain door'. It’s commonly installed at shopfronts, garages, warehouses, and storefronts in urban and commercial areas across China.

Unlike traditional hinged doors, roller shutters provide strong physical protection, weather resistance, and privacy when closed, and can be operated manually with a crank or automatically with an electric motor. They’re especially prevalent in bustling city neighborhoods where small businesses need secure yet space-efficient access control. The term is neutral in register and used in both spoken and written contexts—from maintenance notices to real estate listings.