Product Details: The Hillman Metric Carriage Bolt is designed with coarse threads to fasten a wooden face to either a wood or metal frame. Its flat head is 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. Zinc plating is rust-resistant and provides a beautiful, consistent finish - may not work for all exterior projects M8 diameter x 20mm length This carriage bolt is part of the Hillman Deep Drawer program