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 cabbage, place in a steamer and cook for 5 - 10 minutes until tender but still crisp. To boil, bring a pan of water to the boil, add the prepared cabbage and cook for 5 - 8 minutes until tender but still crisp.