Usually when you are increasing stitches in your knitting you want the increase to be inconspicuous. However, there are times when you want an increase to be decorative, design element. Hence, the open bar increase, or open make 1, or make 1 open, or decorative raised increase. (Why do knitters give stitches so many different names?)
This method can also be used if you forgot to do a yarn over in your work and you don't want to tink, or un-knit, back to the problem. Just be aware that the eyelet created by the open bar increase is slightly smaller than a yarn over eyelet.
Pattern: Wallflower Sweater
Yarn: HiKoo CoBaSi
Needles: skacel by addi Natura Olivewood Circular Knitting Needles