Slide a cotter pin through the hole in the shank to keep a nut from loosening. These screws have a stronger hold than screws with threadlocker or lock washers. They’re twice as strong as low-strength steel screws—use them to fasten most machinery and equipment. All screws have a plating that resists corrosion in wet environments. Length is measured from under the head.

Cadmium-plated screws have a slippery surface to prevent sticking when you tighten or loosen them. Their fine threads are closely spaced for additional vibration resistance. They 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. These screws are made to stringent Army-Navy specifications for performance and reliability.