Wedge is a device that has two or more sloping surfaces that taper either to a sharp edge or to a point. Wedges are used to split or pierce materials, and to adjust the positions of heavy objects. Knives, chisels, axes, pins, needles, and nails are wedges.
A wedge must overcome the resistance of friction as well as the resistance of the material it is being used on. The total resistance may be high enough to require heavy blows from a hammer to drive the wedge forward. The greater the angle between the surfaces of a wedge, the greater the force needed to advance it. If the wedge angle is too great, it is impossible to drive the wedge into the material. The limiting angle varies from 90° to 180°, depending on the amount of friction acting on the wedge surfaces.
