Hex nuts are for general applications and are used with bolts and washers of the same finish. The most commonly used nut they are often found in deck and fence building. The called out size is the inner diameter and the number of threads per inch or thread pitch. Hex nuts are for general applications and are used with bolts and washers of the same finish. The most commonly used nut they are often found in deck and fence building. The called out size is the inner diameter and the number of threads per inch or thread pitch.