Wood will expand and contract across the grain, and a wide panel made of solid wood could change width by a half of an inch, warping the door frame. By allowing the wood panel to float, it can expand and contract without damaging the door.
Put trimmed and cleaned green beans in the steamer basket, set over the boiling water, cover, and steam until tender to the bite, 3 to 5 minutes (depending, again, on how crisp or tender you like your green beans).
To steam fresh fava beans, you need to blanch them first. Bring a pot of water to a boil. Fill a bowl with water and ice. Place the beans in the boiling water for 30 seconds. Drain them and put them in the ice water to halt cooking.