Designed to meet the latest developments in MDF board. Tri-Lock threadform and shank incorporates the benefits of a single coarse thread with a twin thread start on the same screw. Spiral point breaks through the hard, dense surface, allowing the twin thread to engage. The twin thread is reduced to a single coarse thread, enabling high pull-out retention. Underhead ribs for self-countersinking, and Zinc and Yellow-passivated.