- 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.
