A square neck holds these bolts in place to resist turning when fastening with a nut, and the round head provides a smooth finish. Carriage bolts are often used where access to the head is limited.
Grade 8 alloy steel is a high-strength material for demanding applications. It is magnetic.
Grade 5 steel provides good wear resistance and strength. It is magnetic.
Grade 2 and Grade A steels are for light duty use. These materials are magnetic.
Stainless steel has a naturally corrosion-resistant surface that continues to protect the material from environmental contaminants even if scratched. It may be magnetic.