These Square Nuts by Prime-Line Products are constructed of steel and come in a corrosion-resistant zinc-plated finish. They are similar in function to hex nuts, but are 4-sided instead of 6-sided. This shape increases the contact surface, which can help to prevent stripping and loosening in certain applications. They are sometimes used in tight spaces since the square shape allows them to be held in place by adjacent materials, or by use of pliers. Another application is use in metal channels.