What is the term for the vertical enclosure at the rafter tails?

The term "fascia" refers to the vertical board that is installed at the rafter tails, typically at the edge of the roof. It serves both a functional and aesthetic purpose. Functionally, fascia provides support for the lower edge of the roof and helps to hold the gutters in place, protecting the underlying structure from water damage. Aesthetically, it smooths out the transition between the roof and the rest of the structure, giving a finished look to the building.

While sheathing is related to the wooden boards or other material used to cover the rafters and provide structural support for the roof, it does not specifically refer to the vertical enclosure at the rafter tails. The eave is the part of the roof that overhangs the walls of the building, which also does not directly describe the vertical aspect. Gable refers to a specific type of roof shape, characterized by a triangular section at the ends of the building, but again, this does not pertain to vertical enclosures at the rafter tails.

Therefore, the term that accurately describes the vertical enclosure at the rafter tails is indeed fasciа.