Rolling ruler
File:Rolling parallel ruler.jpg
A rolling ruler 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.{{cite book|title=Landscaping: Principles and Practices|author=Jack E. Ingels|chapter=Using Drawing Instruments|publisher=Cengage Learning|date=2003|isbn=9781401834104|pages=11}}{{cite book|title=Measure Twice, Cut Once|author=Jim Tolpin|pages=24|chapter=drawing techniques|publisher=Popular Woodworking Books|date=2007|isbn=9781558708099}}
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. {{US patent|5050309}}