flashing

1. The flashing that covers the joint between a vertical surface and a sloping roof, as at the lower edge […]

1. A color variation on the surface of a brick, produced intentionally or otherwise, due to surface fusion or vitrification

An edge on a metal flashing that is formed to promote the flow of water away from vertical surfaces.

Mortar which provides a weathertight seal in a corner between roofing slates and a wall; used in place of flashing.