Segmental Retaining Walls have been used to build gravity walls for centuries. The modular blocks retaining wall is used for vertical grade changes and can either be a gravity wall or a reinforced soil wall. In a gravity wall the units are stacked up and the weight of the blocks holds the soil in place. In a larger wall that holds a lot of mass a soil reinforced wall might be necessary, which requires the use of geogrids and is typically designed by an engineer. Crown Hill Stone Supply offers segmental retaining walls from the top manufacturers such as Keystone, Versa-Lok, Geowall, and Allen Blocks.