I'm about to head out and play, but here are some images on what I was talking about last night from Hogan's Five Lessons. While I've stated many times I don't agree with a lot of what he says in that book, I do agree with this part.
Also, if you want another perspective on this, The Golfing Machine people refer to this piece as a "pitch elbow." Also, it's the elbow piece used in most Stack and Tilt swings.
You can see how doing this gets your body more involved. Your swing gets less armsy.
Pay no attention to the lines some guy drew on this first pic. I'm just using this to demonstrate how this looks.
Here's the picture from the book. There are a couple pages in there that describe what it does, but the descriptions IMO aren't great. They're better than nothing though.
This improved other pieces in my swing, since like I said, it made me less armsy. Hip sliding and side-tilting became a lot easier on the downswing to accomplish and I could hold the flying wedge for a lot longer with less effort.