Are you talking about leaders and enders like Bonnie Hunter does in Quiltville? In her system when you are chain stitching a bunch of units for a quilt, rather then pulling the last pieced unit and cutting the thread, stitch a HST or two squares together. That is your ender. Next sewing session it is your leader and helps prevent those tiny corners from getting pushed down in the bobbin area. Hope this makes sense. The point behind them is you eventually end up with enough of these HST leaders/enders to make a scrap quilt out of them.