How to Build an Interlocking Wall

Lay a row of blocks along the area where the wall is to be. Cover the front and back with cardboard and spray paint along the path of the blocks.

Dig a trench along the path that is two times the depth of the blocks, and 6 inches wider than the blocks. The trench needs to be as flat-sided and as level at the bottom as you can make it. This can result in some of the trench being deeper in the ground than other areas.

Place stakes every 3 feet along the edge of the path and tie a string along the middle of the stakes if the trench is over 5 feet deep. Put the bubble level on the string to ensure it is level from stake to stake, adjusting the string as necessary and taping it down. Measure downward from the string to the bottom of the trench to ensure a consistent depth is reached.

Tamp the soil down so that it is well compacted. Cover the bottom and sides of the trench with the landscaping fabric and spread gravel to the depth of 1/2 of the blocks. Rake the gravel level.

Set the first block on the edge of the gravel with the face against the front of the soil, followed by the rest of the first row. After each block is set, place the wood stud on the side of it and hit it once or twice to force it firmly against the block on the other side. Stop every few blocks and measure the level. Adjust the gravel as necessary to level the blocks.

Place a half block on the edge of the first row and tap it into place with the maul and wood stud. Continue placing the blocks along the second row until the end, where another half block goes. Check the level every few blocks, but if the first row was level there should be no problem with the second row.

Use a whole block on the third and fifth row starts. The fourth and sixth row starts and ends with a half block. Each block is placed the same a previous ones, with care taken to ensure that it is seated solidly against and above the previous blocks.

Fill in the gap between the wall and the side of the trench with more gravel, taking care that the gravel goes between the blocks and the plastic mulch.