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).
How To Blanch Green Beans: In a large saucepan over medium-high heat, bring water to a gentle boil. Add trimmed green beans and cook, uncovered, 4 to 5 minutes or until crisp-tender (you may need to experiment with the degree of doneness you like). Immediately drain the green beans in a colander and plunge them into ice cold water to bring the temperature down.