Grade 2 square-neck bolts come with a round head and a square neck and are commonly used in wood fastening. The square neck under the round head allows the bolt to set into the hole in the wood to prevent the head from turning. They come in a black oxide finish, which is corrosion resistant in dry environments, or are zinc-plated for corrosion resistance in wet environments. These carriage bolts can also be hot-dipped galvanized (with matching nuts) for added strength, more corrosion resistance than other coatings, and abrasion resistance.

Steel A307 Grade A carbon steel bolts have a square-neck wide head. These step bolts are designed to be used in piping systems with cast iron flanges. These bolts have a square neck that keeps the bolts from turning when the nut is tightened. The bolts' round head provides a finished look and they come in a black oxide finish. Black oxide is corrosion resistant in dry environments.

Grade 5 steel square-neck carriage bolts fasten medium-duty metal-to-metal materials or metal parts to wood. They have a shallow semi-round head and a square neck that prevents the bolt from rotating while the nut is fastened.

Grade 5 ribbed neck carriage bolts are designed for light- to medium-duty fastening projects and come in a zinc-plated finish for corrosion resistance in wet environments.

Grade 8 steel square-neck carriage bolts fasten heavy-duty metal-to-metal materials or metal-to-wood connections. They have shallow semi-round heads and a square body under the head. These bolts come in a black oxide finish that is corrosion resistant in dry environments.

Class 4.6 square neck carriage bolts fasten light-to-medium duty metal parts to metal or metal parts to wood connections. They have shallow semi-round heads and a square body under the head. These bolts have a square neck that keeps the bolts from turning when the nut is tightened. The bolts' round head provides a finished look and they come in a zinc-plated finish for corrosion resistance in wet environments.

18-8 stainless square neck carriage bolts are frequently used to fasten together pressure-treated lumber. They come in a plain finish or are NL-19 coated for corrosion resistance. NL-19 finishes are proprietary treatments that modify the surface of stainless steel fasteners, making them brighter, stronger, and more corrosion-resistant than plain stainless steel. These bolts have a square neck that keeps the bolts from turning when the nut is tightened.

These 316 stainless steel carriage bolts are chemically treated to be more corrosion resistant than 18-8 bolts. They are used to fasten together pressure-treated lumber. These bolts have a square neck that keeps the bolts from turning when the nut is tightened. The bolts' round head provides a finished look, and they come in a black oxide finish.

A2 stainless steel square neck carriage bolts are designed for light-duty fastening. These bolts have a square neck that keeps the bolts from turning when the nut is tightened. The bolts' round head provides a finished look and they come in a black oxide finish. A2 stainless square neck carriage bolts have good chemical resistance and are frequently used to fasten together pressure-treated lumber.