Starrett 4-1/2" master precision square
Starrett catalog number 20-4 1/2.
The finest precision-checking squares - not graduated. Squareness accuracy to .0001" (0.0025 mm) every 6" (150 mm)
These hardened steel squares are used when extreme accuracy is required. The beams and blades are hardened, ground, and lapped to insure parallelism and straightness. The beam is grooved at the inner corner for clearance of burr or dirt. Made of high quality tool steel, with the finest of craftsmanship throughout.
