What an oval vent is
An oval gable vent is an ellipse rather than a circle. Turned upright, it is tall and narrow. Turned on its side, it is wide and low. Both are the same idea: a soft outline without the full height of a circle or the corners of a rectangle.
There is also an oval with keystones, which adds molded keystones on the frame for a more formal version of the same ellipse. All of these are molded high-density polyurethane, factory-primed white, and ready for paint. The material does not rot, and it cuts and fastens much like wood trim.
Where it looks right
A vertical oval suits a tall, narrow gable or a dormer that does not have room for a circle. A horizontal oval suits a long, low gable wall, the kind you see on a rambling cottage or a garage with a shallow pitch. Keystones belong when the door, the windows, or the porch already use them.
Center whichever oval you choose. A vertical oval shoved to one side of a dormer looks like it missed the middle. A horizontal oval should share its center with the gable, not with a single window off to the left.
Open or closed
Air passes only through an open louver. open vertical oval gable vents and open horizontal oval gable vents are the venting versions of the two orientations. closed oval gable vents are decorative, with a solid face behind the slats. If you want the formal frame, look at oval gable vents with keystones as well, and still choose open or closed for the air path. The open versus closed page is the short version of that decision.
A short sizing note
The upright piece shown is LOVO1015, a 10 by 15 inch vertical oval gable vent. The wide piece is LOHO3422, a 34 by 22 inch horizontal oval gable vent. They are not interchangeable. A 10 inch oval will disappear on a 30 foot gable, and a 34 inch oval will overwhelm a dormer. Use the sizing page for a width range based on looks, then check height so the oval clears the rake and the window line.
Pair it with
Pair a vertical oval with a narrow dormer window. Pair a horizontal oval with a long frieze or a row of small windows. Add keystones only if that detail already exists on the house. The install overview shows the difference between an open vent, which needs an opening, and a closed vent, which mounts on the wall.