I dont have that book, darn it! I am not sure if I am understanding what you are not getting but let me give it a shot. After you mark your lines and pull the two edges together, to offset the lines match the first line of one edge to the second line of the other edge. At that line, put a pin on the line 1/4" from the edge then put the pin through the other edge of fabric on the line 1/4"from the edge. That should match up you lines. I hope this makes sense! :-)