Retaining walls can have two purposes. Primarily a retaining wall's purpose is to hold back soil from encroaching on a building or an area, that without such a wall, the slope of the soil would render that area useless. A retaining wall can also prevent erosion and collaspe.

Retaining walls provide support for verticle grade variations. Retaining walls can be made of cement, masonry, brick, steel, and decorative stone. railroad ties in the past were a popular construction material used, but enviornmental factors and the decomposition of the wood have made them an undesirable choice.

The most important thing to remember that with proper design and installation of such a structure is that the material being retained, is attempting to move forward and downslope due to gravity. This on going pressure from behind the wall is dependent on the wall's strength. Pressure at the top of a wall is generally less, whereas at the bottom this pressure is increased, so construction must take these factors into consideration as well as proper drainage which will also cause pressure on the wall.