Sentence:  In Casterbridge there stood a noble pile, .../ But evil days beset that domicile;/ The stately beauties of its roof and wall/ Passed into sordid hands. Condemned to fall/ Were cornice, <WSD>quoin</WSD>, and cove,/ And all that art had wove in antique style. 
Meaning of the word marked with <WSD> tags:  Any of the corner building blocks of a building, usually larger or more ornate than the surrounding blocks.