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by a small rib known as the scoinson rib, and a further development is
given by angle shafts carrying this rib, known as scoinson shafts.
Return
Receding edge of a flat face. On a flat signboard, for example, the re-

turn is the edge which makes up the board's depth.
Revolving Door

An entrance door for excluding drafts from an interior of a building. A
revolving door typically consists of three or four doors that hang on a cen-
ter shaft and rotate around a vertical axis within a round enclosure.

Rib vault
The intersection of two or three barrel vaults.

Roof comb
The structure that tops a pyramid in monumental Mesoamerican archi-
tecture.
Rotunda

A large and high circular hall or room in a building, usually sur-
mounted by a dome.

S

Screens passage
The passage at one end of the Great hall of an English medieval house
or castle, and separated from it by the spere.

Sommer or Summer
Girder or main "summer beam" of a floor: if supported on two storey
posts and open below, also called a "bress" or "breast-summer". Often

found at the centerline of the house to support one end of a joist, and to
bear the weight of the structure above.
Spandrel

The space between two arches or between an arch and a rectangular
enclosure. In a building facade, the space between the top of the window
in one story and the sill of the window in the story above.

Spere
The fixed structure between the great hall and the screens passage in
an English medieval timber house.

Springer
The lowest voussoir on each side of an arch.

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