Location: 08b Windows / Vents (A window)
The width and height of the vent are both tied to the slope. If you change either one, the other is adjusted to maintain the slope.
Frame thickness refers to the box around the louvers.
Mullion thickness: The center mullion, where 0 means no mullion.
Louver parameters: Thickness, Spacing, Angle. The Louver Pen should be thin.
Exterior casing: There are separate widths for the sides and bottom. All parts are the same thickness.
Interior casing: Same options.
Either casing can be turned off. The same Casing Reveal is used for both.
Masonry Cut Depth: Same as a window or door. Sill is drawn with the Masonry Sill Pen, though in most cases you would not see this vent in plan.