panel ovolo single quirk

In architecture, an OVOLO is a round, convex moulding. In Roman work it is usually a quarter circle in section; in Greek work it is flatter, and is equivalent to the echinus; that is, it has in section the elastic curve of the shell of the sea urchin. In mediaeval architecture it is not distinguishable from the multitude of convex mouldings, of all sections, which are used.

In building, a QUIRK is a piece of ground taken out of any regular ground plot or floor, so as to make a court, yard, etc. In architecture a quirk is a small channel, deeply recessed in proportion to its width, used to insulate and give relief to a convex rounded moulding.

[from somewhere on the web]