The ribs that make up the signature corduroy texture.
When it comes to wales, too thick looks old fashioned, but too fine can look like velvet. A medium weight pinwale is your best bet.
Corduroy 511s, $44 by Levi's
Maybe it's the collegiate undertones that come with corduroy, but there's something about this durable cloth that simply screams autumn—or maybe that's just the unmistakable "whoosh" sound of fabric rubbing together.