Arris

Ar·ris

Arris

n.
  1. The sharp edge or salient angle formed by two surfaces meeting each other, whether plane or curved; -- applied particularly to the edges in moldings, and to the raised edges which separate the flutings in a Doric column. (Arch.)

Phrases & Compounds

Arris fillet
a triangular piece of wood used to raise the slates of a roof against a chimney or wall, to throw off the rain.
Arris gutter
a gutter of a V form fixed to the eaves of a building.