It's a funny party gimmick on your snack plate. How to do it: Hard boil an egg. Put the bottom plate into the box and add the egg while it is still warm (not hot). Depending on the size of the egg, put it upright or horizontal/diagonal into the box. Add the top plate on top. With the stamp you push the plate down depending on the size of the egg and lock it in place. Put it into the fridge for 2h. Remove the piston and press the egg out of the box by pressing on the bottom plate. Enjoy square eggs!