diagonal seam tape is simply washi tape that is placed on the front plate of your sewing machine to act as a guide while you are sewing diagonal seams The red thread in the center is aligned with the needle of the machine, the blue thread on both sides is 1/4 inch from the center of the line, representing a 1/4 inch seam edge; just put the tape with the red thread in front of the needle as a needle Trace. Our sewing basting tape is a nice solution for sewing straight diagonal seams without having to mark any lines, a stitch line in red with a seam allowance on either side The seam guide tape is removed cleanly. It is recommended to remove or replace the tape after each item to avoid leaving any residue on your machine. You can choose 2rolls,4rolls,6rolls of sew diagonal seam tapes, enough to meet your various needs in daily life