I have finally figured out how to accurately mark the crosshatch quilting pattern. My blocks are 12" square when finished. I cut them larger and after I completed the applique on each block, I squared them up perfectly, so my measurements are exact. There are twenty blocks around the outside perimeter of the quilt and the quilt is assembled and on my quilt frame. First, with my mechanical pencil, I marked a 1/4" line across the outside raw edge of each block--two sides of the corner blocks and one side of the rest of the blocks--so that I am marking a 12" square block. I determined that with a 1" diagonal crosshatch grid, the lines must begin 1 1/2" apart all around the outside of the block. I then made a pencil mark every 1 1/2" all around the outside of the block. Next, I matched the marks diagonally with my ruler and marked a line, moving across the block, then marking diagonally across the block the other way until the crosshatch grid is complete. This method insures that the next block around the quilt will match up perfectly. Whew! I don't know why it wasn't apparent to me from the beginning how to do this, guess I am just slow.