The tierce is an heraldic ordinary, a vertical band issuant from the dexter side of the shield. As the name implies, it is usually drawn one-third the width of the shield; this proportion may vary, depending on the presence of other charges, or on complex lines of division. The tierce may also be called a “side”; it has no diminutives in Society heraldry.
The tierce may also issue from the sinister, which case is always specified. (Indeed, the dexter tierce is often explicitly blazoned, as well.) The tierce is subject to the normal treatments – embattled, wavy, &c – but like the chief and other single-sided ordinaries, the tierce may not be cotised, voided, dancetty or fimbriated.
We have no unarguable examples of the tierce in period armory; it is found in modern flags, and therefore permitted in Society heraldry. However, because the use of a tierce creates an unbalanced design, the use of a tierce with other charges is a step from period practice, pending documentation. Moreover, since a charged tierce has the additional problem of looking like impaled armory, tierces may no longer be charged in Society armory.
The King of Ansteorra bears as his battle flag: Or, a sinister tierce embattled gules, in canton a mullet of five greater and five lesser points sable.
Charles the Grey of Mooneschadowe bears: Or, a tierce gules.
Diarmait mac Domnaill bears: Bendy sinister azure and argent, a tierce azure.