# How was the first straight edge made?

**URL:** <https://boards.straightdope.com/t/how-was-the-first-straight-edge-made/441082>\
**Category:** Factual Questions\
**Created:** [March 12, 2008, 6:22am UTC](https://boards.straightdope.com/t/how-was-the-first-straight-edge-made/441082 "2008-03-12T06:22:45Z")\
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**Author:** ![rowrrbazzle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rowrrbazzle/32/414_2.png) [@rowrrbazzle](https://boards.straightdope.com/u/rowrrbazzle)\
**Post date:** [March 12, 2008, 7:27pm UTC](https://boards.straightdope.com/t/how-was-the-first-straight-edge-made/441082/16 "2008-03-12T19:27:05Z")

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FYI the earliest known devices to draw theoretically straight lines are the Sarrus linkage and the Peaucellier-Lipkin linkage.

> **[Sarrus linkage](https://en.wikipedia.org/wiki/Sarrus_linkage)**
>
> The Sarrus linkage, invented in 1853 by Pierre Frédéric Sarrus, is a mechanical linkage to convert a limited circular motion to a linear motion or vice versa without reference guideways. It is a spatial six-bar linkage (6R) with two groups of three parallel adjacent joint-axes.
> Although Charles-Nicolas Peaucellier was widely recognized for being the first to invent such a straight-line mechanism, the Sarrus linkage had been invented earlier; however, it was largely unnoticed for a time.
> The Sar...

> **[Peaucellier–Lipkin linkage](https://en.wikipedia.org/wiki/Peaucellier-Lipkin_linkage)**
>
> The Peaucellier–Lipkin linkage (or Peaucellier–Lipkin cell, or Peaucellier–Lipkin inversor), invented in 1864, was the first true planar straight line mechanism – the first planar linkage capable of transforming rotary motion into perfect straight-line motion, and vice versa. It is named after Charles-Nicolas Peaucellier (1832–1913), a French army officer, and Yom Tov Lipman Lipkin (1846–1876), a Lithuanian Jew and son of the famed Rabbi Israel Salanter.
> Until this invention, no planar method ex...

The arms of the Peaucellier-Lipkin linkage don’t have to be straight. Only the indicated distances must be equal. This can be accomplished by stacking those arms and drilling through them all at once.

I’m not sure if an analogous construction method can be used with the Sarrus linkage, but it seems simple enough that the ancients could have discovered it.

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