It was the square head machine bolts that were the industry standard before Hex bolts became prominent. However, presently, square bolts are used largely for aesthetic purposes, offering a rustic finish to a new structure. Besides, they are also used to match existing fasteners of older structures. Square leg screws are also sometimes used to serve such purposes. Machine bolts or cross arm bolts are supplied primarily to the utility industry where they include an added cone point.
Standard Thread Lengths
Bolt lengths < 6″: Thread length = (2 X diameter) + 1/4″
Bolt lengths > 6″: Thread length = (2 X diameter) + 1/2″