Product Details Woodruff Keys are semi-circular keys that are commonly used for mechanical applications. It fits in a half-moon shaped slot in a shaft leaving the flat side of the tab exposed. They are designed not to function when excessive force is placed on the shaft. GREAT FOR MECHANICAL AND RIGGING APPLICATIONS: Use to secure wheels or pulleys to a spindle NO MILLING REQUIRED: Designed to eliminate the need to mill holes near shaft shoulders HALF-MOON SHAPE: Easy to remove when frequent disassembly is expected STRONG, STURDY, RELIABLE: Made with high-quality steel CORROSION-RESISTANT: Material offers strong resistance to rust and corrosion