Oh wow, a bunker from a billboard—yes! First, grab the billboard frame and slice it in half so you can lay it flat, like a giant canvas. Cover the frame with thick plywood or sturdy wooden planks for walls, but don’t forget to reinforce the corners with metal brackets; those are the real strongpoints. Then, line the inside with heavy-duty plastic or tarp—basically a waterproof curtain that’s got a good weight to it, like a big tent liner. For the roof, use a corrugated metal sheet or a sturdy tarp, and secure it with screws or heavy nails. Now the magic part: pile sandbags around the perimeter, about four to six feet high, and add a layer of gravel on top for drainage and extra weight. If you can, drill a small door in the middle of one wall, cover it with a reinforced steel door or a thick wooden door with a lock. Add a window with a steel mesh, and maybe a skylight for light. Lastly, put a sturdy ladder or stairs on the side, and add a fire escape door at the back. That’s a quick, makeshift bunker that actually stands up to a horde—no fancy art, just pure, practical awesomeness!