Usually formed from some type of aggregate and light concrete, retaining wall blocks are sturdy and easy to use. Aggregate is simply a compilation of materials that may include sand, stone and other similar substances, which is used to make up the bulk of the blocks. Retaining wall blocks are excellent for building low walls in the yard or the garden. They are used for both functional and decorative purposes.

The most popular styles of retaining wall blocks are those that interlock and can be assembled without the use of mortar. These blocks are made to fit snugly and create a solid structure without the extra effort and expense of adding mortar. They may be flat on all sides or flat on three sides with one rounded end. The rounded end may be rough or smooth. Many people find curved retaining wall blocks more attractive than other styles, but they also tend to cost a bit more.

Interlocking retaining wall blocks are available in different styles. Those designed for large walls or walls that require a superior degree of soil retention have flanges that fit into niches in another block. For extra sturdiness, some retaining wall blocks have holes through them that are aligned with holes in the block below, through which pins are driven to keep the blocks in place. Others have a simple "lip" or groove along the bottom that partly covers the block underneath it.

Many times, retaining wall blocks are used to create a tiered or stair step design. This type of design works well for sloped yards, not only because it is attractive, but also because it helps create a better system for drainage. Walls must be level, so you must begin with a level surface and continue leveling each layer of retaining wall blocks as you build. You must also backfill each layer of blocks with crushed rock, sand, gravel or soil to make the wall sturdy.

Completing your yard or garden with retaining wall blocks is the perfect project for the do-it-yourself individual or the entire family. While it is a bit demanding physically, it is a simple process. As long as retaining wall blocks are installed properly, the finished effect will be attractive, functional and well worth the effort.