Edge Roller - available from Cleaveland Tools
http://www.cleavelandtool.com/Edge-Forming-Tool/productinfo/EF60/#.V8BaTI71BzY
I interpreted this differently. I believe the line is a marker only, to show where the edges should be broken, not the bottom skin itself. To say it another way, edges are to be broken (upward) aft of the indicated line.