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Find the bottom of your rock shell and turn up side down. Block it so it can't roll. Make mix. Quikcrete or quick wall a little dry and cover the bottom and down the sides a little. This layer will be about 1" thick. I use latex gloves to apply and smooth it. When your applying the mix don't press down to hard or the mix will fall through. Let dry 24 hours. Turn right side and repeat. Let dry 24 hours. At some point you power wash it. Before starting the 2nd layer.