A rubble wall is the most common type of stone wall and is made of stone of random sizes and shapes fitted tightly together when stacked. It is time consuming because a stone must be found that fits just right. We start with a wide base and then narrow the wall at the top. Gravel is compacted into the joints to eliminate voids that could settle later. Natural stone makes a very beautiful wall, but the stone is usually expensive and requires a fair amount of skill.