A long or narrow piece of wood (or another building material) with a triangular cross-section used in various structural applications, specifically one used to raise the tiles or slates of a roof against a chimney or wall.
Origin
Mid 19th century.
Definition of arris fillet in US English:
arris fillet
noun
rare
A long or narrow piece of wood (or another building material) with a triangular cross-section used in various structural applications, specifically one used to raise the tiles or slates of a roof against a chimney or wall.