The figure calls it an imaginary line, but it's not imaginary. It is really only "imaginary" with respect to becoming lots line, as it's not a lot line. But the gap that determines exterior wall fire-resistance ratings and allowable opening percentages is predicated on the gap to this line, as https://spenceridujx.dgbloggers.com/36796584/the-2-minute-rule-for-container-kaufen