Quarry tile– A man-made or machine-made clay tile used to finish a floor or wall. Generally 6″ X  6″  X 1/4″ thick .

Quarter round– A small trim molding that has the cross section of a quarter circle.

Quoin A masonry corner that typically is more massive than surrounding infill of masonry and is made of  or has the appearance of cut stone. Historically, this was used to generate additional strength to a structure.