Double Square, 4" 4R, Starrett
- Starrett 4" double square with graduated blade
- 4R Graduation – 8ths, 16ths, 32nds, 64ths
- Popular with machinists, toolmakers, and patternmakers
The sliding blade is adjustable making it more practical for a wide variety of uses than a common square with fixed blade. The faces of the head are ground square.
Starrett catalog number 13A.
Chris' Tips
When using a precision rule for very close accuracy, the eye can read better by measuring between two lines than from the end of the rule to a line. Here is how to use a steel rule.