It is not possible to dig on [[cliff]] or [[rock tile]]s. Rock tiles can be [[Mining|mined]] down.
To lower a whole [[dirt tile|dirt]], [[moss tile|moss]], [[tundra]], [[steppe tile|steppe]], or [[sand tile]], you must stand in each of the four corners and dig. To raise a tile, you must drop dirt on the tile corners. Clay tiles will lower every 50-100 actions while digging corners. When on tiles like [[peat]] or [[tar]], digging produces material each dig, but will not lower the corner. You must use [[level]]ing for these tiles.
To check if a tile is flat, you can either right-click a tile and select '''[[flattening|Flatten]]''' or examine the tile's borders. If all tile borders say "The [[slope]] is level", then tile is flat. You can also see the difference in height between tile sides by examining the tile's borders. The reference will be a certain number of units of material either away from you or toward you relative to where you are standing. For example, if the slope is 2 dirt steep ''towards'' you, go to the other end of the tile border you examined and dig twice to level the edge in question. To avoid confusion in the beginning when examining tile borders, stand near, or preferably on, the blank non-highlightable "mini-square" at the corner of a tile.