Squares have accurate right angles both inside and outside. Made from a single piece of fully tool steel. Beams and blades are ground and accurately lapped for straightness and parallelism. Blades are beveled on both edges of each side. Beams is grooved at inner comer for clearance of burr and dirt. All squares are fully hardened. Packed in indiviual cartons. Accuracy 0.02 mm.