Knapped flints are flints that have been skillfully worked into squares or rectangles. Generally black or shades of grey, the flint is gauged and laid in courses. Occasionally it is laid randomly, though this is likely to be because the original flint selection was not carried out carefully. The peak use of this style was the 18th Century. Knapped flints are usually laid with tight flushed or recessed joints. Due to its labour intensiveness, high wastage and need for a skilled flint mason, this style was predominantly used on buildings of high status.
Not all flints can be knapped. Because of the need to control and predict the break whilst working, flints sourced from quarries or gravel pits should be used. With the closure of increasing numbers of quarries, good quality raw materials of suitable colour, composition and size have grown scarce, making knapped flint increasingly rare.