In heraldic blazon, a chief is a charge on a coat of arms that takes the form of a band running horizontally across the top edge of the shield. Writers disagree in how much of the shield's surface is to be covered by the chief, ranging from one-fourth to one-third. The former is more likely if the chief is uncharged, that is, if it does not have other objects placed on it. If charged, the chief is typically wider to allow room for the objects drawn there.
Variations of chief
The chief may bear charges and may also be subject to variations of the partition lines. It cannot, however, be cotised. The chief may be combined with another ordinary, such as a pale or a saltire, but is almost never surmounted by another ordinary. The chief will normally be superimposed over a bordure, orle and tressure, if they share the same shield.
A chief impaled (Eton College).
In some medieval and Renaissance drawings of coats of arms, the chief is drawn even deeper, so that it fills almost all the top half of the shield. In some cases, it is drawn so wide that it will look as though the shield is divided party per fess.
A chief triangular can be found in French and English armory. This ordinary begins in the corners and extends to a point that is one quarter to one third the way down the shield. It is a complex line division variant of a chief. A chief enarched is drawn with a concave arch. There is also a double-arched version of a chief.
The chief can be used as a mark of cadency, in order to difference the coat of arms in a minor line of a family, though this is rare and practically confined to cases in which a system of bordures is the usual method of showing cadency and the undifferenced coat of the family already has a bordure. In civic heraldry, a chief of allegiance may be added to the top of the shield, particularly in German heraldry. This is a form of the ruling state's armory compressed into the space of a chief.
In Italy, chiefs are added to the coats of arms of families or locales to indicate political orientation. For example, many Italian coats of arms have a chief containing a version of the arms of the Kingdom of Naples or of the Holy Roman Empire, to denote Guelph or Ghibelline alignment respectively. More recently, a chief gules charged with a fasces, called the Chief of the Lictor, indicated allegiance to the National Fascist Party; it was no longer in use by 1945. 
- A C Fox-Davies A Complete Guide to Heraldry (revised by J P Brooke-Little, Richmond Herald), Thomas Nelson and Sons, London 1969