Due to environmental issues (I'm in a very wet and humid climate area), I primarily use just cinder blocks as they won't rot, sag, rust or lose strength over time like wood or iron. They're cheap enough and tolerate reasonable abuse moving them around. In a few circumstances (very uneven ground), I use cinderblocks with multiple 10' 2x4's to make a stand to hold 5-6 hives (8-frame hives & 5-frame NUC's).