Canton is a square charge

Charge (heraldry)

In heraldry, a charge is any emblem or device occupying the field of an escutcheon . This may be a geometric design or a symbolic representation of a person, animal, plant, object or other device...

 placed in the upper dexter

Dexter and sinister

Dexter and sinister are terms used in heraldry to refer to specific locations in an escutcheon bearing a coat of arms and by extension also to a crest. "Dexter" means to the right from the viewpoint of the bearer of the arms, to the left of that of the viewer...

 corner. It is classed by some heraldic writers as one of the honorable ordinaries

Ordinary (heraldry)

In heraldry, an ordinary is a simple geometrical figure, bounded by straight lines and running from side to side or top to bottom of the shield. There are also some geometric charges known as subordinaries, which have been given lesser status by some heraldic writers, though most have been in use...

; but, strictly speaking, it is a diminutive of the Quarter, being two-thirds the area of that ordinary. However, in the roll of Henry III

Henry III of England

Henry III was the son and successor of John as King of England, reigning for 56 years from 1216 until his death. His contemporaries knew him as Henry of Winchester. He was the first child king in England since the reign of Æthelred the Unready...

 the quarter appears in several coats which in later rolls are blazoned as cantons. The canton, like the quarter, is an early bearing

Bearing

Bearing may refer to:* Bearing , a term for direction* Bearing , a component that separates moving parts and takes a load* Bearing capacity*Bearings, album by Ronnie Montrose in 2000...

, and is always shown with straight lines.

A canton sinister is a canton placed on the sinister side

Dexter and sinister

Dexter and sinister are terms used in heraldry to refer to specific locations in an escutcheon bearing a coat of arms and by extension also to a crest. "Dexter" means to the right from the viewpoint of the bearer of the arms, to the left of that of the viewer...

 of the shield.

The chequer, a pane of the field of chequy, can be considered a diminutive of the canton, though it cannot be a charge on its own.

An "enlarged sinister canton" appears in the arms of William Wilde Lotter.

A plain, uncharged canton (sometimes a canton voided is also used this way) can be used as a mark of distinction, that is, not a mark of peculiar honour, but a mark denoting that the bearer is a stranger in blood. For example a groom, not descended from the bride's family, adopting the bride's last name after the marriage, might upon receipt of a Royal Licence permitting this, use the bride's family's coat of arms with an uncharged canton or canton voided.