Dimension Standards equivalent to ANSI B 18.2.1/ANSI B 18.2.2
Grade 5 bolts have 3 marks or lines on the head that in the shape of a "Y", they could also be described as a postilion of 12 O'clock, 4 O'clock and 8 O'clock
Bolts with hexagon heads and thread are used with a nut or tapped hole