Bar sinister

In heraldry, a bend is a band or strap running from the upper dexter (the bearer's right side and the viewer's left) corner of the shield to the lower sinister (the bearer's left side, and the viewer's right). Authorities differ as to how much of the field it should cover, ranging from one-fifth (if shown between other charges) up to one-third (if charged alone). The supposed rule that a bend should occupy a maximum of one-third of the field appears to exclude the possibility of two or three bends being shown together, but contrary examples exist. Outside of heraldry, the term "bend (or bar) sinister" is sometimes used to imply ancestral illegitimacy.

A bend can be modified by most of the lines of partition, such as the bend engrailed in the ancient arms of Fortescue and the bend wavy in the ancient coat of Wallop, Earls of Portsmouth.

The usual bend is occasionally called a bend dexter when it needs to contrast with the bend sinister, which runs in the other direction, like a sash worn diagonally from the left shoulder (Latin sinister means left). The bend sinister and its diminutives such as the baton sinister are rare as an independent motif; they occur more often as marks of distinction. The term "bar sinister", is an erroneous term when used in this context, since the "bar" in heraldry refers to a horizontal line.

The bend sinister, reduced in size to that of a bendlet or baton, was one of the commonest brisures (differences) added to the arms of illegitimate offspring of European aristocratic lords. A narrow bendlet or baton sinister was the usual mark used to identify illegitimate descendants of the English royal family dating from fifteenth century. For example, Arthur Plantagenet, 1st Viscount Lisle (d.1542), illegitimate son of Edward IV of England, bore the arms of the House of York with a bendlet sinister overall. The full-sized bend sinister was seldom used in this way, and more recent examples also exist of bends sinister that have no connection with illegitimacy, such as in the arms of the Burne-Jones baronets.

...
Wikipedia