Which of the following terms refers to the horizontal layers of materials laid in roofing?

The term that refers to the horizontal layers of materials laid in roofing is "courses." In roofing, courses are typically used to describe the rows or layers of shingles or tiles that are installed horizontally across the roof surface. Each course contributes to the overall water-shedding capability of the roof, as they overlap each other to prevent water from penetrating through the seams.

Flashing, on the other hand, is a critical component used to direct water away from joints and features of the roof, such as valleys, chimneys, and vents. While it plays an important role in ensuring the roof's integrity, it does not refer to the horizontal layers.

Cornices are architectural elements along the roof's eave or at the top of walls that typically add aesthetic value rather than referring to the roofing layers themselves.

Trusses are structural supports used in the framework of a building or roof system, providing stability and shape but not describing the layers of roofing materials.

Understanding "courses" is essential in roof installation and repair, as the way these materials are layered impacts the overall performance and durability of the roofing system.