Rolling ruler

A rolling parallel ruler

Antique rolling rulers

A rolling ruler (also known as a parallel glider) is a ruler that contains a cylinder much like a rolling pin inside, thereby enabling it to "roll" along a sheet of paper or other surface where it is being used. A rolling ruler can draw straight, parallel lines, and also has other instruments included, enabling it to do the jobs of a protractor and compass. ^{[1] [2]}

The modern rolling ruler, with protractor, pivot pin and multiple pin holes serving as fixed length compasses has been patented in the US in 1991 by Wei Wang. ^[3]

References

1. Jack E. Ingels (2003). "Using Drawing Instruments". Landscaping: Principles and Practices. Cengage Learning. p. 11. ISBN   9781401834104.
2. Jim Tolpin (2007). "drawing techniques". Measure Twice, Cut Once. Popular Woodworking Books. p. 24. ISBN   9781558708099.
3. U.S. patent 5,050,309