caps before becoming officially mandated as a uniform item. In NATO Joint Military Symbology a yellow quatrefoil represents a unit or object whose allegiance is unknown. Societies The quatrefoil is the official symbol of the Bishop James Madison Society, est. 1812 at the College of William and Mary. Fraternity The quatrefoil is also the symbol of the women's fraternity Phi Mu (a member of the National Panhellenic Conference). See also Foil (architecture) Trefoil References External links Pictures of Ghiberti's and Brunelleschi's quatrefoils Roman, Mars, "The Fancy Shape (Episode 106)." 99% Invisible. PRX, 17 March 2014. web: 21 March 2014. Ornaments Christian symbols Architectural elements Heraldic charges Visual motifs Piecewise-circular curves