A flat is a residential unit that stretches from the front to the back of a building on a single floor. A building with flats has no lobby or public corridors; each flat has its own entry either from the exterior or from a common staircase at the front. Flats generally come in variations of standard types with either two, three, four, or six flats in the building. In two- and three-flats buildings, the units are normally stacked on top of each other and each is entered from a door that opens onto the street. In four- and six-flats buildings, there is a symmetrical arrangement with either two parallel stacks of two flats each or two parallel stacks of three flats each; these are both served by a common central staircase at the front with a window or balcony at each landing, leading to the name Romeo flats. According to Albert Armstrong, a prolific builder of flats during the reconstruction boom: “It looks as though the three, four, and five-room apartment flat is to be the most popular dwelling in San Francisco . . . There is more money to be made from these flats than from the six and seven room ones.” (San Francisco Call, 22 January 1908) Flats are multi-unit versions of urban rowhouses in which each building largely fills its lot (or leaves ten feet or more of open space at the rear) and abuts its side neighbors. Many also encroach on the public space by projecting bay windows. Because of the necessity under the law of providing natural light and ventilation to every room in buildings built side by side, small light courts or light wells are built on the sides of flats. This requirement generates a standard size and floor plan. Each flat has a long straight hall down one side from the front door. Flats usually have four rooms: the front and back room are exposed to light and air through windows in exterior walls; the two interior rooms and the bathroom (or rooms, when the toilet and bath are separated), are exposed to light and air through a small light court part way back on the side of the building. Some flats are narrowed at the rear with a set back from the side lot line, permitting light from windows on the slot; this is a back end version of the front end “slot”, identified by Delehanty in San Francisco Victorians (Delehanty 1991:132, 133) Each flat is thus in an asymmetrical floor plan that might be described as a half barbell, with wider rooms at the front and the back of the unit and narrower rooms in the center at the light court. In four- and six-flats buildings where there are two flats on each floor, the overall plan, with plans of two adjacent flats in mirror images of each other, might be described as a full barbell. Because of the way most of the buildings were inhabited – families, extended families of four to eight or more people with children or lodgers or both – the three front rooms were commonly used as bedrooms, also a front room with a bay window would often be labeled “parlor” on plans. The back room was a kitchen. In addition, behind the kitchen was a porch, of lighter construction than the main building and with more window area, allowing light to enter the kitchen; sometimes this was referred to as a “cooking porch”, although the stove and its flue was always within the main kitchen space. A rear stairway led down from the kitchen to a basement, used for winemaking, garbage, and storage. In later years, basements of early flats buildings were often modified for use as parking garages. Flats buildings built in the 1920s were often built with parking garages included in the basements. *Delehanty, Randolph. 1997. In the Victorian Style. San Francisco: Chronicle Books.