Vesica piscis in the context of "Mandorla"

In heraldry, an escutcheon (/ɪˈskʌtʃən/, ih-SKUTCH-ən) is a shield that forms the main or focal element in an achievement of arms. The word can be used in two related senses. In the first sense, an escutcheon is the shield upon which a coat of arms is displayed. In the second sense, an escutcheon can itself be a charge within a coat of arms.

Escutcheon shapes are derived from actual shields that were used by knights in combat, and thus are varied and developed by region and by era. Since shields have been regarded as military equipment appropriate for men only, British ladies customarily bear their arms upon a lozenge, or diamond-shape, while clergymen and ladies in continental Europe bear their arms upon a cartouche, or oval. Other shapes are also in use, such as the roundel commonly used for arms granted to Aboriginal Canadians by the Canadian Heraldic Authority, or the Nguni shield used in African heraldry (likewise, Christian organisations and Masonic bodies tend to use the same shape, also known as a vesica piscis).

In geometry, a lemon is a geometric shape that is constructed as the surface of revolution of a circular arc of angle less than half of a full circle rotated about an axis passing through the endpoints of the lens (or arc). The surface of revolution of the complementary arc of the same circle, through the same axis, is called an apple.

The apple and lemon together make up a spindle torus (or self-crossing torus or self-intersecting torus). The lemon forms the boundary of a convex set, while its surrounding apple is non-convex.