the distance between the edge of a slate and the edge of the slate it part covers in the preceeding course.

The longitudinal overlap of adjoining materials.

The horizontal distance one shingle overlaps adjacent shingle in the same course; also the horizontal distance one sheet of roofing overlaps adjacent sheet. French (Chevauchement latéral)

A term used to describe the lap at the side or lengthwise direction of panels.

A horizontal lap