Gusset

Was at first a piece of chain, and afterwards of plate-armor, intended as a protection to the vulnerable point where the defenses of the arm and breast left a gap. In heraldry it is one of the abatements, or marks of disgrace for unknightly conduct. It is represented by a straight line extending diagonally from the dexter or sinister chief point one-third acro the shield, and then descending perpendicularly to the base.