A border one fifth the width of the shield, surrounding the field. It is usually plain, but may be charged.

A broad band at and along the outer edges of a FIELD.

A border at the edge of a shield

a border around a shield, and engrailed means indented along the edge with small curves

Narrow border

In heraldry, a bordure is a contrasting border around a shield, traditionally one-sixth as wide as the shield itself.