Extension find the soft/smooth edge between two materials

Just now saw it was for soften smooth. I do not have one of those I will add that to my list.

I don’t know what to tell you. It was about 15 minutes from the time I got your file until I had it fixed and I first had to get myself acquainted with the file.

I went all the way across there looking for gaps time and time again and did not find it until I started sectioning it off.

Last question: is there a way to avoid sketchup automatically softening and smoothing edges in the first place? Or is that the turning soft smooth to 0?

As I told you before, setting Softening to 0 will prevent it. If you do that for the whole model, it’ll be difficult to manage because all of the edges will be visible.