When referring to bullnose, it is sometimes modified by adding the word quarter of half. In the illustration, one piece of quarter-bullnose tile is juxtaposed with a plain piece of tile, to create a finished look - note that the top trim strip shows a quarter-bullnose on two of its sides.
However, when referring to counter tops (such as a granite counter top in a kitchen) which extends beyond the edge of the underlying cabinetry, either a quarter-bullnose of half-bullnose edge my be used. A half-bullnose can be contructed by bonding two sections with quarter-bullnose, effectively creating a 180-degree curve, in order to create a more finished appearance. This would effectively double the thickness of that portion which extends beyond the cabinetry.