Hillman 832522 Stainless Steel Carriage Bolt, 1/4 x 2-1/2-Inch, 25-Pack Carriage Bolts are designed to fasten a wooden face to either wood or metal Flat head provides a semi-flush finish to applications The heads is designed to eliminate the need for a washer Square underside of the head is self locking to eliminate the need for a driving tool Stainless Steel provided superior rust prevention and bright finish