I moved into a house once where someone had left a king-size headboard, one that was made like a long bookshelf. I painted it a bright yellow to go with some other bright colors I was using on furniture on the front porch. I used it there as a bench and a plant prop. After a few years, I got tired of it, but wanted to make something different from it, so I took it out the front, dug a small hole and placed it standing on it's end in the front yard and then planted monkey-paw vines on it. It took off and was covered in vines before too long. If I had had 3 king-size headboards, I would have placed two standing beside each other and then placed the 3rd headboard on top of the others to make an arbor for the vines.