I have used many things to mark my quilt tops for quilting, but these days I use a Hera Marker most frequently. For straight line quilting I used to use painter’s tape. I would mark the line across the quilt with a length of this tape and stitch beside it. It works great. Until it doesn’t. Sometimes I accidentally stitch over the edge of the tape and I’m left looking for tweezers to pull the little pieces of tape off.