Drawing on a vertical surface

 From:  George (GKSL4)
Hi Michael,

Very nice interface, excellent program. I spent at least half an hour everyday playing around with Moi. Very promicing.

I have a small question. (I search forum but I didn't found an answer). I attach a small file trying to draw a freeline on a vertical surface, but I cannot keep points on it. Only if I rotate parallel to front or right view I can do it. Is there a tip how to draw without rotating?