This is a really neat seam that becomes invisible when the sewing thread is drawn up. It utilizes the horizontal bars between the first and second rows of the edge of the fabric.
Place the two pieces of stockinette fabric side by side, right side up. Use a yarn needle threaded with matching yarn (we have used contrasting yarn for clarity) to pick up the first two horizontal bars on the righthand piece of fabric.
Draw the needle through and then proceed to pick up the first two horizontal bars on the lefthand piece of fabric. Make sure you are working in one full stitch from the edge.
Continue in this process until you have worked up both pieces of fabric. The stitches will cross back and forth between the two.
When you have finished sewing, you can grasp the sewing thread and tug gently on it to even out the seam. It should draw the two pieces of knitting together, creating a seamless appearance.