Wisine Brand Square Head Bolt ,the head design of square head bolts enables an easier wrench grip for nut tightening. They are usually used in new consyruction to mimic an older aesthetic or in railway applications.Square head machine bolts were the industry standard prior to hex bolts gaining prominence. Square bolts are now most commonly used for aesthetic purposes to provide a rustic look in a new structure or to match existing fasteners in an older structure. Square lag screws are also used for these purposes.square bolts from 1/2″ diameter through 2″ diameter in most ASTM, AASHTO, and SAE specifications. Special tooling can be created to produce nonstandard head dimensions or bolt heads with your company’s name and/or logo.