• 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.