The Avery tool is on the left and the Clevand tool is on the right. Most people don't like the Avery tool. It's less precise in that the amount of roll depends on the angle you maintain while rolling. Also it tends to stretch the skin making it wavey. The Clevlend tool gives a conststant roll and does not wave the skin near as much.
The clevland tool overlaps the skin mush more then the Avery tool. So, if you want to roll an edge that has dimpled holes close to the edge then the Clevland tool is out. The Avery tool does not over lap the skin nearly as much. But it's still too much when you've dimpled holes close to the edge. On an aileron skin where I forgot to roll before I dimpled, I used the Avery tool with a small modification. I cut a popcycle stick so that I could push it between the rollers. The rollers are raised so the stick did not affect the rollers. But, it did move the rollers closer to the edge of the skin while using it. The rollers just cleared the dimples. Oh good.
I was ready to toss the Avery tool but now I've discovered a use. But, the better idea is to roll with the Clevland tool before you dimple.
