A door is a movable barrier that closes an entrance or room. It provides privacy, security, climate control, and fire separation. Doors are also a design element: their size, material, and hardware affect how a space feels and functions.

There are many types. A hinged door swings on hinges. A sliding door moves along a track. A folding door collapses in sections. A revolving door allows continuous traffic while maintaining a seal. Each has advantages and limitations.

Doors in commercial buildings must meet code requirements for fire rating, egress width, and accessibility. A fire door must close and latch automatically. An accessible door must have a clear opening width and operable hardware that does not require tight grasping or twisting.

Hardware matters more than people think. A beautiful door with a cheap closer will slam. A heavy door with the wrong hinge will sag. Specifying door hardware is a specialty in itself, and good architects pay attention to it.