hello everyone. I was hoping someone could point me in the right direction. I've had my room plastered and now want to put the coving up. I have got all materials required for the job. I have just started marking my line on the wall and celing. It is 67mm to the edge of my cove. The problem is that if i go 67mm all around the room and mark my straight line it tends to float because i assume the celing is not quite level. Do I go to my 67mm all around or do i just make sure the lines are level right around the room. Its my first attempt and i've prepared properly and just want to do a propper job. Hope someone can help... Cheers