Sentence:  The cavities or cells run horizontally, and the blocks are dovetailed together at the joints, and united with strong-guaged plaster of Paris and lime putty, or air-slacked lime. They are <WSD>set fair</WSD>, and dressed with scrapers, forming a surface suitable either for paint or paper. 
Meaning of the word marked with <WSD> tags:  (masonry) To provide a smooth, finished surface on plaster after roughing in.