Wedge

The wedge: a ramp that moves

Push it in, and it pushes things apart. Or holds them together.

How this site works. Every fact is in our own words and linked to its source, beside it. Where good sources disagree, we show each version in a “Sources differ” box.

A wedge tapers to a thin edge. Push it one way and it pushes sideways. Britannica

A wedge is really two inclined planes back to back. Science Trek

Push a wedge in one direction and it pushes sideways (our drawing).Drawing: our own, simplified and not to scale

Wedges split, lift and tighten, for example to fix a hammer head onto its handle. Britannica

A black-and-white photo of a group of men in a forest standing on and beside a huge felled log split with wedges — Splitting a spruce log with wedges, Washington State, around 1918.Picture: Clark Kinsey, Public domain, via Wikimedia Commons (cropped and resized)

Splitting and cutting

Wedges were used in prehistoric times to split logs and rocks. For rocks, wooden wedges were wetted so they would swell. Britannica

An axe is a wedge, and so are the teeth on a saw. Britannica

Knives, axes, needles, scissor blades and ice picks are wedges that separate. Science Trek

Holding things together

Wedges also hold things in place: staples, drawing pins, nails, doorstops and shims. Science Trek

The zip

A zip uses two ancient tools, the wedge and the hook: the slide holds a set of wedges that push the teeth together or force them apart. Indiana Public Media

A close-up of a small metal zip slider with its pull tab — A zip slider: inside it, wedges push the teeth together going up and apart going down.Picture: Rolf Dietrich Brecher, CC BY 2.0, via Wikimedia Commons (cropped and resized)

Scissors are a compound machine: the edges of the blades are wedges, joined to make a lever. Science Trek

Next: the screw →