Whatever works best at your disposal. I have the yellow Lego blocks but often prefer just to shovel a few inches of sandy soil topped with a inch thick layer of leaves, works great, is all natural and cheap too. For bumpy rocky boondocking parks the sand method may not be too practical and the Legos may not set right. I've found some nice flat stones and even well shape split logs do the trick as well. Also if leveling with Legos on a dirt or grassy surface, padding them with leaves at the base does wonders when it's time to pack up. Otherwise those things get impacted with dirt and grass. The leaves bang out real easy. A cheap stablizer in the rear does well with stopping the shaking jerky motion, especially when doing the wildthang in the back.