I used a bending brake, but if you do not have access to one you could clamp a 2 X 4 over the bend line on your workbench and then with everything clamped tight , use another 2 X 4 just over the edge and push down across the entire span. If you could hinge the two 2 X 4s together at the bottom would work best. Something like a piano hinge with the hinge point recessed into the 2 X 4s.
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.
The edges indicated on 28-02 overlay the bottom skin on the aft fuselage. Take a look at page 29-02 and you'll see why it makes sense to only break those edges.
Also, typically when they want you to bend something they will show how much to bend by either giving a specific angle or having you match it against an existing assembly.
Mike is right, it works well, but beware - Adjust it so that the clamping pressure is fairly light even if you have to do a couple of passes. It has a tendency to ride up or slip so go slow and be careful.
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.
The note says "break edges upward aft of this line". It is not directing to make a bend on this line (or it would have said bend at the indicated line).