Key pattern is the generic term for an interlocking geometric motif made from straight lines or bars that intersect to form rectilinear spiral shapes.^[1][2][3] According to Allen and Anderson, the negative space between the lines or bars of a key pattern “resemb[es] the L- or T-shaped slots in an ordinary key to allow it to pass the wards of the lock.”^[4]

Key patterns have been discovered and used in ornamentation by a number of global cultures in human history, and are thought to largely have been designed independently of each other.^[4][5] The earliest examples of key patterns are seen in textile ornaments from Mezin, Ukraine, dated to approximately 23,000 B.C.^[5][6][7] Key patterns were also common in textile and ceramic ornamentation during the Neolithic period, with examples found among archeological discoveries in present-day Fiji, Peru, Mexico, Moldova, Romania, Hungary, Yugoslavia, and Greece,^[4][5][6][7] as well as in pre-Christian Celtic art.^[1][2][3] The oldest known pair of pants, wool trousers found in a grave dated to approximately 1038-926 B.C. in present-day western China, have a decorative band of key patterns woven into them.^[8] In addition, extant examples of early medieval Insular art, such as stone decorations and illuminated manuscripts, as well as Japanese, Chinese, and Islamic decorative arts from different periods, feature key patterns.^{[3][4][9][10]}

Celtic mazes, Greek frets, and xicalcoliuhquis are examples of well-known designs that are considered to be key patterns.^[2][4][11]

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  Key patterns forming a border in the Roman Mosaic of Dioscorides as seen in the Handbook of Archaeology, Egyptian - Greek - Etruscan - Roman (1867)
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  Key patterns seen in architectural details at El Tajín, a pre-Columbian archaeological site in southern Mexico.
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  A detail of key patterns from a Greek painted terracotta amphora from 8th century B.C. in the collection of the Archaeological Museum of Athens
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  A fragment of an engaged column carved from limestone, with key patterns, rosettes, and acanthus leaves, from a 6th-century monastic community in Bawit, Egypt.
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  A fragment from a limestone frieze with diagonal key patterns and rosettes from 6th century Byzantine Egypt, in the collection of the Metropolitan Museum of Art.
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  Rectilinear key patterns seen among other ornaments on a bronze Chinese cooking vessel from the Shang dynasty.
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  A decorative paper sheet with paisley and Greek key patterns printed in relief from 18th century Italy in the collection of the Metropolitan Museum of Art.
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  A wool rug ca.1900-1920 from the Navajo people in the Early Crystal style, with key patterns forming the outer border.
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  Vintage Japanese designs of key patterns from The Practical Decorator and Ornamentist by G.A & M.A. Audsley
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  Vintage Japanese border designs using key patterns from The Practical Decorator and Ornamentist by G.A & M.A. Audsley
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  Antique Greek border designs of key patterns and other ornaments from The Practical Decorator and Ornamentist by G.A & M.A. Audsley
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  Variations in decorative key patterns from the Handbook of Ornament; A Grammar of Art, Industrial and Architectural Designing in All Its Branches, for Practical as well as Theoretical Use (1900)
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  Cushion Cover, 17th century. Kongo textiles, Kongo peoples; The Kingdom of Kongo. Ethnographic Museum, Stockholm.