I'm trying to describe the wrinkles between one's pair of eyebrows that the person's unconsciously making. Here are what I've come up with:
He's making wrinkles between his eyebrows.
He's frowning through his eyebrows.
He's frowning with his eyebrows.
I've never used any of these lines before so I don't know which of them is natural to native speakers or if any of them convey the meaning I'm trying to express. Note that the person isn't really "frowning" and the only noticeable thing on his face is the wrinkles between his eyebrows.