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).
1 Heat a pot of salted water to a rolling boil (1 Tbsp salt for 2 quarts of water). Add the green beans and boil them for 4-5 minutes, until just tender enough to eat (you may have to cook longer depending on the particular green beans you have). Drain and set aside.