7/16x1 1/4 UNF SET FULL THRD BL GR8 LEFT HAND 3/4 AF
Left-hand threads are the opposite of right-hand threads.
Their threads run in the anti-clockwise direction and must be turned anticlockwise to fasten them or clockwise to unfasten them.
Thread = 20 TPI Hexagon head Across the Flats ( AF ) = 3/4"