The bottom-left room has a separate pitched roof, pitched in all 4 directions. I drew lines to form two triangles and then joined them with the blue line, the ridge line of the roof. It looks OK but when I try to move that line, it will move in any direction except the up/blue axis. Whatever I do I can’t get that as the inference, it keeps looking right then I rotate and realise it’s just a perspective trick:
Is there a way to force this to do what I want? And is the fact I’m having problems indicative that I’m doing something fundamentally wrong, or is it just part of learning the tool?
Closer fiddling seems to indicate something is locked/blocking this motion. Some side-effect of faces and lines auto-joining I suspect, meaning my model is doing something I cannot see with the naked eye.
Move + Alt - to force the move by ‘auto-folding’ some connected faces if necessary, otherwise the movement could be prevented in that axis by connected geometry…
Here is an example, in this case you haven’t broken the corners so even following the edge still moves the selection along the wrong axis, but as soon as you hit alt you get the corner folds that allow the selection to move up.