Sometimes it's a hassle to have to uncoil the tape measure, line it up against the fabric, and count out 13/32 to mark a spot. Especially if you have to do it multiple times, say for measuring the distance between bone casings or marking how long embroidery stitches must be. A tailor's shuriken is the weapon of choice for these situations. Just rotate the disc to the desired measurement and hold it to the fabric. Easy peasy.
I can not vouch for the accuracy of this as a throwing star, only as a measuring device. I also can not vouch for the accuracy of the term "tailor's shuriken." There could be another name for this tool. I wouldn't use it though.