According to the stress mode of the connection, it is divided into ordinary and hinged holes. According to the shape of the head, it can be divided into hexagonal head, round head, square head, countersunk head, and so on. Hexagonal heads are the most commonly used. Generally, countersunk heads are used where connections are required.

The horseback bolt, also known as U-bolt, is a non-standard component with a U-shaped shape. It has threads at both ends that can be combined with nuts and is mainly used to fix tubular objects such as water pipes or sheet objects such as car springs. Due to the way it is fixed like a person riding a horse, it is called a horseback bolt. According to the length of the thread, it is divided into two categories: full thread and non full thread.

According to the tooth shape of the thread, it is divided into two types: coarse tooth and fine tooth, and the coarse tooth shape is not displayed in the marking of the bolt. Bolts are divided into eight grades based on their performance levels: 3.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, and 12.9. Among them, bolts above grade 8.8 (including grade 8.8) are made of low-carbon alloy steel or medium carbon steel and undergo heat treatment (quenching+tempering), commonly referred to as high-strength bolts, while bolts below grade 8.8 (excluding grade 8.8) are commonly referred to as ordinary bolts.

Ordinary bolts can be divided into three grades according to their manufacturing accuracy: A, B, and C. Grade A and B are refined bolts, while Grade C is rough bolts. For connecting bolts used in steel structures, unless otherwise specified, they are generally ordinary rough grade C bolts. There are differences in the processing methods of different levels, and the corresponding processing methods are usually as follows: ① The bolt rods of grade A and B bolts are processed by a lathe, with a smooth surface and precise dimensions. Their material performance level is 8.8, and their production and installation are complex and expensive, which are rarely used; ② Grade C bolts are made of unprocessed round steel, and their dimensions are not precise enough. Their material performance level is 4.6 or 4.8. During shear connection, the deformation is large, but the installation is convenient and the production cost is low. It is mostly used for tensile connection or temporary fixation during installation.