In heraldry, a gusset is a charge resembling the union of a pile with a pale extending from chief to base (or in the case of a flag typically resembling the union of a pile and a fess extending from hoist to fly). In French heraldry, it has been classed as one of the thirty honorable ordinaries.[1] For an 'inverted' gusset, one issuing from base and extending to the chief, some authors prefer the term graft.[2]
Other heraldic traditions conceive of the gusset not as this central charge but as a "line of truncation of the field",[3] a flank-like charge similar to the gore or flaunch. A pair of gussets defined this way produce said central form as negative space between them upon the field. Heraldic writers in these traditions describe the gusset as 'line of truncation of the field' as "a traverse line"[4] extending diagonally from the dexter or sinister point of the chief across one-third of the field, then descending in a straight line orthogonal to the base.[5]