"The blocks, which are technically known as voussoirs, should be of a wedge shape, the center or top block being the keystone A; the lower blocks B B which rest on the supporting pier are the springers, the upper surface of which is called the skewback, C C; the side blocks, as D, are termed the hauches. The lower surface or soffit of the arch is the intrados, E, and the upper surface the entrados, F. The rise of the arch is the distance from the springing to the soffit, G, the width between the springers is called the span, H, and the radius I. The triangular spaces between the arches are termed spandrils, K." — The Encyclopedia Britannica, 1910

Arch

"The blocks, which are technically known as voussoirs, should be of a wedge shape, the center or top…

"Three center arches, employed in French Flamboyant." — The Encyclopedia Britannica, 1910

Center Arch

"Three center arches, employed in French Flamboyant." — The Encyclopedia Britannica, 1910

"Four center arches, employed in the Perpendicular and Tudor periods." — The Encyclopedia Britannica, 1910

Center Arch

"Four center arches, employed in the Perpendicular and Tudor periods." — The Encyclopedia Britannica,…

"Cusped arch; Christchurch Priory, Hants." — The Encyclopedia Britannica, 1910

Cusped Arch

"Cusped arch; Christchurch Priory, Hants." — The Encyclopedia Britannica, 1910

The mask decoration was founded in Pompeii, Rome. These masks were used as keystone decorations of doors and window arches.

Mask Decoration

The mask decoration was founded in Pompeii, Rome. These masks were used as keystone decorations of doors…

The mask decoration was found in Pompeii, Rome. These masks were used as keystone decorations of doors and window arches.

SideMask Decoration

The mask decoration was found in Pompeii, Rome. These masks were used as keystone decorations of doors…

"Drop arches, with centers within the arch." — The Encyclopedia Britannica, 1910

Drop Arch

"Drop arches, with centers within the arch." — The Encyclopedia Britannica, 1910

"Upright elliptical arch, sometimes called the egg-shaped arch, employed in Egyptian and Sassanian architecture." — The Encyclopedia Britannica, 1910

Elliptical Arch

"Upright elliptical arch, sometimes called the egg-shaped arch, employed in Egyptian and Sassanian architecture."…

"Equilateral pointed arches, described from two centers, the radius being the whole width of the arch." — The Encyclopedia Britannica, 1910

Equilateral Arch

"Equilateral pointed arches, described from two centers, the radius being the whole width of the arch."…

"Flat arch, where the soffit is horizontal and sometimes slightly cambered (dotted line)." — The Encyclopedia Britannica, 1910

Flat Arch

"Flat arch, where the soffit is horizontal and sometimes slightly cambered (dotted line)." — The…

"Pointed foiled arches, in the arcades of Beverley Minister and Netley Abbey." — The Encyclopedia Britannica, 1910

Foiled Arch

"Pointed foiled arches, in the arcades of Beverley Minister and Netley Abbey." — The Encyclopedia…

"Horseshoe arch, with the center above the springing; employed in Moorish architecture." — The Encyclopedia Britannica, 1910

Horseshoe Arch

"Horseshoe arch, with the center above the springing; employed in Moorish architecture." — The…

"Pointed horseshoe arches, found in the mosque of Tulun, Cairo, 9th century." — The Encyclopedia Britannica, 1910

Horseshoe Arch

"Pointed horseshoe arches, found in the mosque of Tulun, Cairo, 9th century." — The Encyclopedia…

"Lancet arches, with centers outside the arch." — The Encyclopedia Britannica, 1910

Lancet Arch

"Lancet arches, with centers outside the arch." — The Encyclopedia Britannica, 1910

The Keystone mask is a Graeco Italic design that is made out of terracotta.

Keystone Mask

The Keystone mask is a Graeco Italic design that is made out of terracotta.

"Multifoil cusped arch, invented by the Moors at Cordova in the 10th century." — The Encyclopedia Britannica, 1910

Multifoil Arch

"Multifoil cusped arch, invented by the Moors at Cordova in the 10th century." — The Encyclopedia…

"Ogee arches, with curves of counter flexure, found in English Decorated and French Flamboyant." — The Encyclopedia Britannica, 1910

Ogee Arch

"Ogee arches, with curves of counter flexure, found in English Decorated and French Flamboyant." —…

The state banner of Pennsylvania, the keystone state.

Pennsylvania

The state banner of Pennsylvania, the keystone state.

A printers quoin is a device for locking up or fastening type in chases or galleys.

Printers Quoin

A printers quoin is a device for locking up or fastening type in chases or galleys.

Arch of Titus.

Roman Arch

Arch of Titus.

"Segmental arch, where the center is below the springing." — The Encyclopedia Britannica, 1910

Segmental Arch

"Segmental arch, where the center is below the springing." — The Encyclopedia Britannica, 1910

"Semicircular arch, he center of which is in the same line with its springers." — The Encyclopedia Britannica, 1910

Semicircular Arch

"Semicircular arch, he center of which is in the same line with its springers." — The Encyclopedia…

"Stilted arches, where the center is below the springing, but the sides are carried down vertically." — The Encyclopedia Britannica, 1910

Stilted Arch

"Stilted arches, where the center is below the springing, but the sides are carried down vertically."…