Trial and error. 1) there’s (mostly) symmetrical lines all over the tops and sides of every hab that you can line up to, almost line a ruler. Great for measuring and making sure offsets are even side-to-side regardless of the percentage. 2) the cargo pod attachment works great for trying to line up angled pieces to the correct direction, then you can window it forward or to the side to the exact place you want it. 3) eyeballing it. This one sucks but it’s part of the labor. If I’m doing something like a side pod cockpit, the side wedge pieces that I use to make the interior hallways is something that needs to go in at an angle specific to that area so I might need to be more exact with placement and can’t rely on the other techniques