1. Flange bolts: These bolts have a built-in washer-like flange under the bolt head, which provides a larger bearing surface and helps distribute the load. They are commonly used in automotive and construction applications.

2. Shoulder bolts: Also known as stripper bolts, these bolts have a cylindrical shoulder beneath the head that acts as a guide or bearing surface. They are often used in rotating or sliding applications, such as machinery or automotive components.

3. Square head bolts: These bolts have a square-shaped head instead of the typical hexagonal shape. The square head allows for greater torque application and can be useful in applications where a wrench or pliers are used to tighten or loosen the bolt.

4. Step bolts: These bolts have a series of steps or varying diameters along the shank. They are used in applications where different components need to be fastened at different depths or where spacing is required.

5. J-bolts: These bolts have a J-shaped hook on one end and a threaded shaft on the other. They are commonly used for anchoring purposes, such as securing posts or poles into concrete.

6. U-bolts: These bolts have a U-shaped bend with threaded ends on each leg. They are often used to secure pipes, rods, or other cylindrical objects to a surface.