Identify a round kitchen tool with perforated and hinged metal leaves
It's a steamer basket.

If you pull the leaves apart it will look like this:



Then you put it into a saucepan like this:



You put water into the saucepan (the legs at the bottom keep the bottom of the basket clear of the water). Then you can use it for steaming vegetables, dumplings, etc. You put a lid onto the saucepan to keep the steam in.