There's every chance in the world that I'm using it wrong, but my "simple observation skills" tell me that I can turn the adjuster clockwise for ten minutes and nothing visible will happen. Then I can turn the adjuster anti-clockwise for twenty minutes and still nothing visible will happen. It never comes to a "stop". Not even the amount of metal ferrel (?) showing at both ends of the plastic barrel changes. If I hold the brake lever down, I can't turn the barrel adjuster either way. That's why I thought the mechanism itself might be broken, or that I had previously unscrewed something inside beyond the point of no return. I really don't know how the mechanism works in order to shorten or lengthen the cable. (or have that effect, anyway). I can take it to my LBS or I can buy a replacement and take this adjuster out and dissect it to understand how the mechanism works, but like I said, I'd rather be riding! But I'm still optimistic that I'll get the understanding I need from Bike Forum.