Flint that has been knapped to give a straight edge on top, bottom, right and left sides. This was very
time-consuming for the mason, and hence expensive for the client. Found rarely, and only on most prestigious sites.
The example shown below is visible only from within the Choir House garden, an area not normally open to the public. Here the flint is both squared and coursed (laid in even horizontal rows).
Local example (click to enlarge)
Cathedral precincts, Choir House (formerly Table Hall)