A decorative use of flint on the walls of buildings. In this the flints are knapped to expose the inner colour of the flint (usually black, but sometimes grey or brown) and set in the walls with the flat smooth surface outermost. In some cases the flints are shaped into squares to fit together to make large smooth panels. In others the flints are fitted into recesses in limestone blocks to make patterns and lettering, the black knapped flints contrasting with the white of the limestone (the flints are fitted to be flush with the surface of the limestone, hence the term flushwork). In a minority of cases the flints are combined with bricks.Flushwork appears suddenly in the early 14th century, with the gatehouse of Butley Priory being both one of the earliest and most magnificent examples. It was used extensively in the 15th and early 16th centuries on churches throughout East Anglia.