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).
Cover the lid and reduce the heat to low so that the water will simmer. Steam the beans for three to five minutes. After about four minutes, pull one of the beans out and taste it. The beans are ready when they are bright green and somewhat crunchy. If the beans are too hard, then cook them for another one to two minutes.