Dynamite is cheap.

If you don't have yer powderman's papers and yer on bedrock, just add four anchors, two lengths of wire rope and two turnbuckles and Bob's yer uncle. If I was down there, I could make a mint goin door-ta-door selling and installing them on accounta I don't expect everyone's got a rock drill. I'd have two models. A Plain Jane and one with seats on a raised floor. Then there's accesories... survival kits, crank radio, crank lantern, chloride tablets, Winchester Defender 13 (fer yer looters), lots a stuff... anybody got any more crazy ideas?