Grillage consists of a set of pallets interlaced with a set of barrulets; it is essentially a fretty field set crosswise. Strangways’ Book, c.1450, blazons it as “square fretty” and assigns it to the arms of Sir John Mandeville [H. Stanford London, Some Medieval Treatises on English Heraldry, 1953, p.178].
Like fretty, while grillage has some of the characteristics of a field treatment, it acts as a charge: charges overlying grillage must have good contrast with the underlying field.
The Canton of Forestgate bears: Vert, a bear rampant sustaining a key within a laurel wreath Or and a chief Or grillage sable.
Avisa of Dun Carraig bears: Azure grillage Or, on a bend sinister argent two forget-me-not sprigs stems to center azure slipped and leaved vert.
Cristoffel Muller bears: Azure grillage Or, on a chief argent two castles gules.