This double stitch marker is both a ring marker and locking progress keeper. 

To use as a progress keeper, push the bird's tail (it's a lever!)on its side to open the clasp. Hook the marker to a stitch in your work to highlight a stitch or note your place in your work. 

To use as a stitch marker, slip the attached ring onto your knitting needle, in between live stitches, to mark a specific place in your work.