Hex Head Bolts with an Integral Serrated Washer
Flange bolts have hexagonal heads, designed to be driven by a wrench. The unique characteristic of Flange Bolts is the design of the head, from which they get their name. The "flange" of the bolt is a built in (integral) washer. In Imperial sizes, this washer is serrated to act as a lock washer.
Flange bolts are available in both full thread and partial thread varieties. The threading depends upon the lengths of the bolt. Partially threaded flange bolts have a shoulder, and fully threaded flange bolts are threaded to the underside of the flanged head.