Flange bolts are available at websites specializing in nuts and bolts, such as Fastenal and FlangeBolts.com, and are also available at major online retailers, such as Amazon.com. Flange bolts are also typically available at most hardware stores, such as Lowe's.
Flange bolts have a flanged hex and a built-in washer to help distribute the clamping load. Flange bolts are typically used in combination with hex flange nuts. The bolt is designed to create a larger distribution area to help alleviate pressure. Flange bolts come in a variety of styles, and some of the most common are grade five and grade eight bolts.