I'm doing a 3D sketch, just a line drawing at present. With the line tool I use the TAB key to select which plane I'm drawing in (XY, YZ, YX etc). But whichever plane I draw the line on it is not contrained to the plane. So even though I dimension the line it is still underdefined. I'm having to then select the plane and the line and add a parallel relationship between them, but this is long and I've been told to avoid parallel relationships in 3D sketches. So does drawing a line along a plane not fix it to the plane?