Kreg Zinc Screws are a good choice for a wide variety of indoor projects with limited exposure to the elements. Available in a variety of sizes, thread options, head styles, and quantities. Steel Kreg Screws are case hardened, a process that forms a tough outer shell (or case) to make the screw durable, but keeps the core softer to prevent the screw from becoming brittle. That means you get the best of both worlds: a strong screw that won’t snap. Fine threaded screws are designed for hardwoods. Maxi-Loc screws have a large head giving maximum clamping of the joint to bring the two pieces together, making for a very strong joint.