Hillman Hot Dipped Galvanized Steel Carriage Bolt 1/2 in. Dia. x 8 in. LSave the day and prevent a breakdown by installing these Hillman Carriage Bolts on your next project today! The Hillman bolts are designed to fasten a wooden face to either a wood or metal frame. They have a flat head designed to eliminate the need for a washer and provide a semi flush finish to applications. The square underside of the head is self locking to eliminate spinning and the need for a driving tool. These flat head carriage bolt's