Now I've sewn all of the cording and placed it on my cutting table. This great little tool allows you to rotary-cut or mark your choice of 4 different piping seam allowances. For my application, I chose the 3/8 inch seam allowance. Just place piping on the mat and align the groove of the ruler for the seam allowance you wish to use.
And cut away! Look how perfect that seam allowance is! I just love it.
And here you see about 3 yards of gorgeous piping for the inside of my jean jacket. Oh, I do have a suggestion that is not in the instructions. LOL. If you have a cat that loves to play with strings, I suggest you shoo them from the room until you're done cutting. You can give them the scraps from cutting your lovely, neat piping.