A Stitch marker tool
A stitch marker is used when knitting and crocheting and is often in use when a diagram is followed or when you are knitting around. It's a way to indicate where a tour starts (or ends) so you can easily see where one started. When you follow a diagram it is also useful: set the pattern repeats every 10 stitches, then place a stitch marker between stitch 10 and 11, and you can repeat every 10 stitches. If you lost count, you just have to count (or pull out) a few stitches.