Once in a while, I use the flatlocking feature on the serger to join pieces of batting together. I do several pieces at a time. The pieces lay flat nicely without any puckers or excess fabric on one side. I've tried the interlocking foot on the DSM (the stitches go back and forth both sides of the seam). It works, but it does not always lay flat for me. Now, there are iron on tapes (in two widths) for joining pieces of batting together. Works well.