I just like to clarify things for other students. When you scale zero in y on the edge loops to add "ding" detail on the big rectangular brackets, first make sure that your pivot point to median. Then ctrl-r to make the edge loop and left click immediately. Then s-y-0 to scale zero in y. After that you used the move gizmo (or "g" key) to move the edge loop. If I have trouble, someone else probably is, too, right?
