When segments of a continuous fascia meet at a corner, they miter. You can specify the mitering option: vertical, horizontal, or perpendicular.
A fascia does not miter with other existing fascias, even if they meet at the corners.
Roof Fascia panel

Vertical miter

Horizontal miter

Perpendicular miter
Roof fascias can miter between the eave and rake edges of a plumb-cut gable roof.
