Considering a geologic fault that is non-vertical, there are two blocks moving next to each other. One has shifted up while the other has shifted down down. The hanging wall is the block that has moved upward, which is above the fault plane; and the footwall is the block that has moved downward.

In mining applications, it is important to know where the hanging wall and footwall occur. Often, vein deposits (e.g., metal or diamond deposits) can occur within the fault zone between the hanging wall and footwall. Thus, we are often mining ore that is between these two blocks.

When possible, openings are driven into the footwall in order to better ensure good ground and roof control. When openings are in the hanging wall, roof bolting or other means of roof and rib support are often needed.

Figure: Hanging wall and footwall.