I have one of those beds that used ropes. I ended up drilling holes in the iron side rails and added 2x4s to support a box spring. When you stack a box and a modern mattress on a bed that wasn't designed for that, you end up with a sleeping platform that's about 40 inches above the floor! And it wasn't easy getting a 21st-century mattress to fit on a 19th-century frame, but I love the finished product.
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