Solar parabolic cooker with the mechanical mathematician!

Step 2 Cutting the lines

This was a square box , it has 4 segments. I divided it lengthwise into 3 equal pieces using 2 lines (in yellow), I scribed them a little, cut with the sissors to extent the cuts to them and bent it over at the lines to mark the line bend into the cardboard.
This gives 12 little same sized rectangles in the box.