TM 9-2815-250-24&P E-6.  FASTENER GRADE. In addition to being classified by thread type, thread fasteners are also classified by material.  The most familiar fastener classification system is the SAE grading system (Table E-5). Table E-5.  SAE Screw and Bolt Markings SCREWS BOLTS SAE GRADE 2 SAE GRADE 6 NO MARKING 4 RADIAL DASHES 90 APART SAE GRADE 3 2 RADIAL DASHES SAE GRADE 7 180 APART 5 RADIAL DASHES 72 APART SAE GRADE 5 3 RADIAL DASHES SAE GRADE 8 120 APART 6 RADIAL DASHES 60 APART Markings on Hex Locknuts GRADE A - No Marks GRADE A - No Marks GRADE B - 3 Marks GRADE B - Letter B GRADE C - 6 Marks GRADE C - Letter C GRADE A - No Notches GRADE B - 1 Notch GRADE C - 2 Notches E-5/(E-6 blank)