The Foundation

• 1). Clear debris and uproot plants if necessary.
  
  
• 2). Dig a trench that's 6 feet deep and 28 inches wide, using a shovel.
  
  
• 3). Tie the 4-foot level to a two-by-four and test the trench. If the air bubble is not between the safety lines, deepen the trench or add backfill to level it out.
  
  
• 4). Fill the trench with gravel and then compact it, using a tamper. When you're done, the gravel should be roughly 1 inch from the top of the trench.
  
  
• 5). Cover the gravel with 1/2 inch of sand. Level the sand with a screed board. Once it's flat, you're ready to start laying cinder blocks.
  
  

The Cinder Blocks

• 1). Lay the first level of bricks, ensuring that they're tightly packed.
  
  
• 2). Lay the 4-foot level across them. If they are not level, backfill or remove sand as necessary. Afterward, test each individual block front-to-back and adjust.
  
  
• 3). Fill the trench with soil. This will lock the blocks in place.
  
  
• 4). Lay the next row of cinder blocks. Do not place them directly on top of the blocks below, but instead place them over the cracks between blocks. This improves wall stability.
  
  
• 5). Hammer the pins in through the pin slots with a mallet until they're flush with the block's surface. This locks the blocks in place. Repeat this process all the way to the top of the wall. For aesthetic purposes, use special "cap" cinder blocks at the top.