(not really a hint, since it's what @ffao has already effectively done above, and presumably what (s)he's trying to do now): If someone took the time to do all steps cleanly and just skip step 8, it may be a little more obvious
since it would otherwise be painful monkey work and not "puzzling" - the square with the open circle should only end up with a line on the right, not both sides and as per my comment earlier (@Deusovi) you dropped your half line on the filled "*" square again...
For what it's worth, I did my "test" version on paper so that it's impossible to mix things up. :) but yeah, thicker lines would've likely made it less error prone too