I have this model. I want the selected edge to match the red line. Is it possible to do this without turning the model and using sx0?
I am using 2.79b and there's CTRL+S > to hit for "Cursor to active" if an edge or a vertex point is selected in Edit mode. There's also CTRL+S > "selection to cursor" for once the edge or a vertex point to be moved to cursor once they're selected/ I assume the red line is something parented to the camera if I'm not wrong. And I believe You could boolean a line in the helmet with it, and then move the rest of the needed verts to the cut line, followed by selection of the cut line to dissolve it once the vertex points and edges has been moved. Options for CTRL+S works with edges, as well as vertex points, so I bet that by moving verts, You could move the whole edge pretty precisely.