About 25% stronger than medium-strength steel heavy hex head screws, these screws hold up to the high stress of joining I-beams and scaffolds. Also known as structural bolts, they meet ASTM A490 and 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 standards for dimensions. Length is measured from under the head.

Steel screws are best for dry environments, since moisture will cause them to rust. They require little surface prep before applying a finish, so you can apply your own paint or coating. To meet structural standards, use these screws with plain steel structural nuts 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 plain steel screws. To meet structural standards, use these screws with zinc-flake-coated structural nuts (sold separately) and washers.

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 exposed to sideways force.