I am putting in a raised bed garden using 2 rows of concrete blocks. My garden bed is 8x4 feet and it took 20 blocks to complete the bottom row. I am staggering the second row of blocks on top. To make it more stable, I am putting 1 foot long pieces of 4" PVC pipe in the holes to lock them in place. I will then fill the holes with dirt and grow herbs. It will make it easy to move if that is what I want in the future.