The tressure is an oridinary that echoes the outer edge of the shield, being a thin single or double line somewhat inset from the outside. It can decorated at key points with fleurs-de-lys in which case it is known as a tressure flory counter-flory. A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1894, Entry:tressure Wade considers it to be the emblem of “preservation and protection”, presumably because of its “surrounding” of the other charges. The Symbolisms of Heraldry, W. Cecil Wade, George Redway, London, 1898 P51