These are strips that keep reams of paper, the lids on the boxes, are handy to use as 1/4" reference tool for markings. They are very handy for placing at the bottom edge of fabric to stop and pivot when sewing on binding on corners. Line it up horizontally with the bottom edge as you sew towards the bottom and stop sewing when you reach the white strip. Place your needle in the "down" position, pivot, fold the edge to the top, lineup the raw edges and sew. When you come to the edge, is thin enough that if you accidentally stitch into it, it will not break your needle. These can be picked up at a stationary store, hardware store, local office that uses paper and are usually no charge.