A wedge is two inclined planes joined together. When joined, the inclined planes form a sharp edge. Inclined planes are stationary objects, whereas wedges are active objects. When force is applied to the flat side of the wedge opposite the sharp edge, parts of the object become separated. For example, an ax is a metal wedge that splits a piece of wood apart. Readers will be provided with a number of examples of wedges, where they're found, and the wedge's historical uses.