The fit Singer, bed mount. This was the typical Greist set sold for to fit Singer machines. The bed holes are not in the right spot for these to work with any of my top clamp feet machines.
Here is what the complete set looks like, and another style that also fits Singer and low shank side mount feet machines.
on your picture, that long thing in the front is a door slide - or what ever it's called. It mounts on the door and then the slide part hooks into something on the cabinet, so you can't open the door past that point.