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).
Place a lid over the colander to evenly cook the vegetables. For added flavor, place lemon zest or fresh herbs, such as basil or parsley, in the boiling water. Steam green beans for about five minutes, or until they reach the desired tenderness.