# Dictionary Definition

straightedge n : hand tool consisting of a flat
rigid rectangular bar (metal or wood) that can be used to draw
straight lines (or test their straightness)

# User Contributed Dictionary

### Adjective

- Living one's life against/without the use of alcohol, smoking, and illegal drugs.

### Noun

- A tool which is flat, rectangular and commonly made of wood, metal or plastic and is used to draw, cut or check the straightness of straight lines.

# Extensive Definition

- For the subculture, see Straight edge.

A straightedge is a tool similar to a ruler, but without markings.

## Compass-and-straightedge construction

An idealized straightedge is used in compass-and-straightedge constructions in plane geometry. It may be used:- Given two points, to draw the line connecting them.
- Given a point and a circle, to draw either tangent.
- Given two circles, to draw any of their common tangents.

It is possible to do all compass and straightedge
constructions without the straightedge. That is, it is possible,
using only a compass, to find the intersection of two lines given
two points on each, and to find the tangent points to circles. It
is not, however, possible to do all constructions using only a
straightedge. It is possible to do them with straightedge alone
given one circle and its center.

## References

- Wayne R. Moore, Foundations of Mechanical Accuracy, Moore Special Tool Company, Bridgeport, CT (1970)

## External links

straightedge in German: Haarlineal

straightedge in Persian: ستاره (ریاضی)

straightedge in Swedish:
Rätskiva