Carriage bolts are a type of fastener commonly used in woodworking and construction. They have a smooth, rounded head and a square section just below the head, which helps prevent the bolt from turning when tightened. Typically made of steel, they are available in various sizes and lengths to suit different applications. These bolts are often used in conjunction with a nut and washer to secure materials together, such as wood or metal. Their design allows for easy installation, making them a popular choice for projects like building furniture or assembling decks.