Editing Keystone (architecture)

{{Short description|Wedge-shaped stone at the apex of a masonry arch}}{{About|the architectural element||Keystone (disambiguation)}}
{{Redirect|Key stone}}
[[File:L-Karniesbogen (keystone).png|thumb|The keystone (shown in red) of an arch]]
[[File:Entrance of Colditz Castle chapel.jpg|thumb|Dropped keystone at [[Colditz Castle]]]]

A  '''keystone''' (or '''capstone''') is the wedge-shaped stone at the [[apex (geometry)|apex]] of a masonry [[arch]] or typically round-shaped one at the apex of a [[Vault (architecture)|vault]].  In both cases it is the final piece placed during construction and locks all the stones into position, allowing the arch or vault to bear weight.<ref name=ching>{{cite book | last = Ching | first = Francis D.K. | title = A Visual Dictionary of Architecture | publisher = John Wiley & Sons, Inc. | year = 1995 | location = New York | pages = 12 | isbn = 0-471-28451-3 }}</ref><ref>{{cite web |url= http://www.pitt.edu/~medart/menuglossary/keystone.htm |title= Glossary of Medieval Art and Architecture – Keystone |publisher= [[University of Pittsburgh]] |access-date= 2007-06-25 }}</ref><ref name="merriam">{{cite web |url= http://www.merriam-webster.com/dictionary/keystone |title= keystone |publisher=Merriam Webster |access-date= 2007-06-25 }}</ref> In arches and vaults (such as quasi-domes) keystones are often enlarged beyond the structural requirements and decorated. A variant in domes and crowning vaults is a [[lantern (architecture)|lantern]]. A portion of the arch surrounding the keystone is called a [[Crown (arch)|crown]].{{sfn | Wilkins | 1879 | p=292}}

Keystones or their suggested form are sometimes placed for decorative effect in the centre of the flat top of doors, recesses and windows, so as to form an upward projection of a [[lintel]], as a hallmark of strength or good architecture.

Although a masonry arch or vault cannot be self-supporting until the keystone is placed, the keystone experiences the least stress of any of the [[voussoir]]s, due to its position at the apex.{{citation needed|date=April 2022}} Old keystones can decay due to [[weathering]] and vibration, a condition known as [[bald arch]].

==Architecture==
In a [[Rib vault|rib-vaulted]] ceiling, keystones commonly mark the intersections of any two or more arched ribs.  For aesthetics, keystones are often larger than ribs in vaults and many of the [[voussoir]]s (arch stones) in arches, or embellished with a [[boss (architecture)|boss]]. 

A "dropped keystone" is one where the keystone projects lower than the other voussoirs. Following [[Giulio Romano (painter)|Giulio Romano]], [[Mannerism|Mannerist]] architects of the 16th century often designed arches with enlarged and slightly dropped keystones, as in the "church house" entrance portal at [[Colditz Castle]]. Numerous examples are found in the work of [[Sebastiano Serlio]], a 16th-century Italian Mannerist architect.

==Metaphor==
{{see also|cornerstone}}
Keystone is often used metaphorically for an essential part on which the whole depends or as an acme of the whole.

In Christianity, [[Psalms]] 118:22,<ref>{{Bible|Ps|118:22}}</ref> translated in the [[Authorized Version]] as "The stone which the builders refused is become the head stone of the corner", is taken to refer to Jesus.

The [[List of states and territories of the United States|U.S. state]] of [[Pennsylvania]] calls itself the "Keystone State", because during early American history, it held a crucial central position among the [[Thirteen Colonies]] geographically, economically, and politically, like the keystone in an arch.<ref>{{cite web |title=State Symbols |url=https://www.pa.gov/guides/state-symbols |website=PA.gov |publisher=Commonwealth of Pennsylvania |access-date=12 January 2024}}</ref> A keystone is a symbol of Pennsylvania, being used in the logos of many Pennsylvania government departments, in Pennsylvania [[Highway shield|state route signs]], and on [[Vehicle registration plates of Pennsylvania|Pennsylvania car license plates]], and the Shoulder Sleeve Insignia of the Pennsylvania National Guard's [[28th Infantry Division (United States)]], a Red Keystone, first adopted during [[World War I]] in October 1918.

Referring to the [[Book of Mormon]], [[Joseph Smith]] said that it "was the most correct of any book on earth, and the keystone of our religion, and a man would get nearer to God by abiding by its precepts, than by any other book."<ref>{{cite book |title=[[History of the Church (book)|History of the Church]]'' Volume 4'' |date=1908 |publisher=[[Deseret News]] |location=[[Salt Lake City]] |page=461 |access-date=12 January 2024 |chapter=Chapter 27 |chapter-url=https://byustudies.byu.edu/online-chapters/volume-4-chapter-27/}}</ref> [[Ezra Taft Benson]], the 13th president of [[the Church of Jesus Christ of Latter-day Saints]], said it "is my prayer that the Book of Mormon may become the keystone of our lives."<ref>{{cite news |title='Keystone of our religion' |url=https://www.thechurchnews.com/2013/8/17/23224107/keystone-of-our-religion |access-date=12 January 2024 |work=[[Church News]] |date=17 August 2013 |language=en}}</ref>

== Gallery ==
<gallery mode="packed" heights="150px">
Image:8500 - Milano - Palazzo Borgazzi (1829) - Dettaglio - Foto Giovanni Dall'Orto, 31-Aug-2007.jpg|Keystone from the palazzo Borgazzi ([[Milan]], [[Italy]])
File:Barcelona. Generalitat Palace. Door to Carrer del Bisbe. C. 1638. Pere Pau Ferrer, architect. (18966422650) (cropped).jpg|Keystone much enlarged for decorative effect, and carrying a coat of arms, [[Barcelona]]
Image:Chapter House ceiling (crop 1).jpg|The York Minster Chapter House rib-vault ceiling with central and peripheral keystones 
File:Middle keystone in the Chapel of St. Anne in Malbork showing Jesus Christ.jpg|A [[boss (architecture)|boss]] depicting [[Jesus Christ]] decorates the keystone in the rib-vaulting at Chapel of St. Anne in [[Malbork]], 14th century.
Image:Toulouse Cathedral - Keystone 1.jpg|[[Boss (architecture)|Boss]]ed keystone in the ceiling of an apse chapel ([[Toulouse Cathedral]])
Image:Spain Andalusia Cordoba BW 2015-10-27 13-54-14.jpg|[[Horseshoe arches]] with equal-size [[voussoirs]] and [[keystones]], [[Mosque–Cathedral of Córdoba]], [[Spain]]
1993-1994-Giardino Giusti (Verona)-testo e photo Paolo Villa-nA2-tesi Accademia Belle Arti Bologna-portone di Palazzo Giusti.jpg|Main entrance Giusti's Palace Keystone, with rustic [[quoins]] and [[face]] of man
File:Bonn-Oberkassel Alte Evangelische Kirche Schlussstein.jpg|Dropped keystone on a German church
File:München-Altstadt Rumfordstraße 23 490.jpg|Doors and windows with decorated keystones, [[Munich]]
File:Tor der Casa di Giulio Romano.JPG|A range of plain but enlarged keystones by [[Giulio Romano (painter)|Giulio Romano]] for his house in [[Mantua]]
File:Mark Master Keystone.gif|The keystone is the symbol of the [[Order of Mark Master Masons]]
File:Navicular bone12.png|As a metaphor, the [[navicular bone]], shown in green, is known as the keystone of the foot<ref>{{Cite web |title=UpToDate |url=https://www.uptodate.com/contents/stress-fractures-of-the-tarsal-foot-navicular |access-date=2022-06-11 |website=www.uptodate.com}}</ref>
</gallery>

== See also ==
* [[Architectural sculpture]]
* [[Coping (architecture)]]
* [[List of classical architecture terms]]
* [[Oculus (architecture)|Oculus]] compression ring

==Notes==
{{Reflist}}

== Sources ==
* {{cite book | last=Wilkins | first=H.S.C. | title=A treatise on mountain roads, live loads, and bridges | publisher=E. & F.N. Spon | year=1879 | url=https://books.google.com/books?id=f9DNAAAAMAAJ&pg=PA291 | access-date=2023-12-16}}

== External links ==
{{EB1911 poster|Keystone}}
{{Commons category-inline|Keystones|lcfirst=yes}}

{{Authority control}}

[[Category:Arches and vaults]]
[[Category:Ornaments (architecture)]]
[[Category:Architectural elements]]