I had a pile in a two bin system and the material rested on a wire grid 4" off the ground (think of it as a floor in the bin). The wire was stapled to 2 x 4's and I had a piece of rebar in the middle to help support the weight. I would then use a 4' piece of rebar to make holes every 4" through the pile. As the material heated in the pile (grass clippings and carbons) this would draw fresh air into the pile. The temperature got to 160 in short order. The wire grid on the bottom had a short lifespan but worked great to aerate the pile.