The most commonly used heavy hex head screw, these medium-strength steel screws are strong enough to join I-beams and scaffolding. They meet ASTM A325 and ASTM F3125 standards for structural applications. Since the head is 10% wider than a standard hex head, it spreads force over a larger area, and you can tighten these screws with more torque. All screws meet ASME B18.2.6 specifications for dimensions. Length is measured from under the head.

Partially threaded screws have a precisely measured unthreaded section under the head, called a grip. It’s stronger than the threaded section, so you can place it in joints subjected to sideways force.

Steel screws are best for dry environments, since moisture will cause them to rust. They are easier to paint than hot-dipped galvanized screws because they require less surface prep. To meet structural standards, use these screws with plain steel structural nuts and washers.

Hot-dipped galvanized steel screws have a thick coating for excellent corrosion resistance. Since the finish is thicker than other finishes, these screws are compatible with only hot-dipped galvanized steel fasteners. To maintain their corrosion resistance and meet structural standards, use them with hot-dipped galvanized structural nuts (sold separately) and washers.

Zinc-flake-coated steel screws have a multilayer finish that resists mild chemicals and provides long-term corrosion resistance. They stand up to 720 hours of salt spray per ASTM B117 standards. They also meet ASTM F3393 specifications for appearance and performance. An embedded lubricant makes these screws easier to install than hot-dipped galvanized screws. To maintain their corrosion resistance and meet structural standards, use them with zinc-flake-coated structural nuts (sold separately) and washers.