The YUKON™ screw is a strong Structural Lag screw with a 5/16 Hex Head for a powerful torque transmission and easy installation. The built-in washer underneath the head provides great holding power and works well for heavy duty applications. The Twin Blades set of knurls cuts fast to dramiatically reduce friction and heat on the shank, while reducing load on the drill. They also provide better performance by removing debris faster than a standard fastener's knurl. The Sharp threads allow for immediate grip for a faster start and reduces splitting.