These are my wall scratchings near the spot where the line will pass through the wall and into the stairwell. I needed the benchwork to be about 30mm lower than the lowest point of this. As the line could have passed either above or below the noggin (the cross brace) that sits inconveniently at pretty much the exact height I want the trains to run at I had to decide to either go over or under this or cut it out. Going under meant a vertical deviation of 25mm whereas going over would have meant a grade rising about 110mm. The decision made itself.