Foil is an architectural device based on a symmetrical rendering of leaf shapes, defined by overlapping circles that produce a series of cusps to make a lobe[1]. Typically, the number of cusps can be three (trefoil), four (quatrefoil) or five (cinquefoil).
Bellairs Corpus[]
- Changes to the Cathedral of Saint Gorboduc in the Thirteenth Century included cinquefoiled ogees (Saint Fidgeta and Other Parodies; 34).