1.1 ,This specification covers the chemical and mechanical requirements of hexagon and square-head zinc-coated steel bolts and atmospheric corrosion-resistant bolts, in nominal thread diameters of ¹/₂ ,, ⁵/₈ ,, ³/₄ ,, ⁷/₈ ,and 1 in. for use in the construction of transmission towers, substations, and similar steel structures. The various types of bolts covered in this specification are: