•      A wedge consists of two inclined planes that meet at a sharp edge.

•      Wedges are often used to cut or split objects.

•      People have been using wedges in Africa since the earliest Stone Age, about 2.6 million years ago.

•      These early wedges were stone hand-axes, and their sharp edges let people cut a hunk of meat off a gazelle to eat, or cut branches for firewood.

•      Probably people also used wooden wedges to split bigger pieces of wood into smaller pieces.

•      A thick short wedge will split things apart faster, but we'll have to push down on it with more force – maybe if we hit it with a hammer.

•      A thin long wedge will be easier to drive in, but it will take longer to split something.


Figure 72: Chisel, an iron wedge (sledge hammer), knife, hacksaw blade

•      Today we have many different uses for wedges. A plow is a kind of wedge.

•      A knife is a kind of wedge, and a fork is made of four little wedges.

•      Razors and scissors are wedges too. A nail is a kind of wedge, and so is the pointed nose of an aero plane that helps it cut through the air more efficiently.

Figure 73: Pin, crocodile and shark tooth, old knitting needles

•      Wedges are used as either separating or holding devices.

•      A wedge can either be composed of one or two inclined planes.

•      A double wedge can be thought of as two inclined planes joined together with their sloping surfaces outward.