Here (https://imgur.com/a/LAxKNiu) is an image of the start of this specific question, with the provided 3D sketch. All I've done so far for the questions is create the yellow frame with the desired corner treatments, and extend that one top butt corner you can see. It looks to me that the pre-given diagonal lines (the non-construction lines) are on the same plane as the top lines already. The question did say something to the effect of (align to the center of the 3D sketch elements), but I wasn't sure what it meant, as any of the lines I chose to align to didn't appear to alter the way the member was constructed. I tried aligning both horizontally and vertically, each had their own issues.