Minecraft wiki entry for Walls_and_buttresses, associated text: A retaining wall is a wall that prevents earth, sand, gravel, or snow from flowing down a slope. They result in a significant difference in the height of the ground on either side of the wall. There are several ways to implement a retaining wall but there are few visible differences between them because the parts that are different are usually buried. It's also possible to combine the following designs in various ways.