GRK's RSS Rugged Structural™ Screw is made of specially hardened steel to provide high tensile, torque and shear strength. The sharp threads and points bite instantly into the material (including hardwood), reducing the splitting effect due to smaller shanks. RSS Rugged Structural™ screws have a six threaded CEE thread that enlarges the screw hole for the non-threaded portion of the fastener, allowing the wood to settle easily and increasing the screw's drawing strength. The CEE thread also reduces the friction on the screw shank which can result in lowering the driving torque and the likelihood of splitting the wood. This is why the RSS Rugged Structural screw is an efficient lag screw alternative. The round head with built-in shield (washer type head) has no sharp edges like conventional lag screws. The added shoulder (nominal diameter) underneath the washer has the ability to center the RSS Rugged Structural™ screw in pre-drilled hardware like hinges and connector plates. Additional features include recessed Star Drive: Zero stripping, with 6 points of contact; Cee Thread: Enlarges hole to reduce splitting; W-Cut™: Low torque, smoother drive; Zip-Tip™: No pre-drilling, faster penetration; Washer Head: for immense holding power; Cutting Pockets: provide a clean hole and reduces splitting, and bore with precision; ESR-2442 Approved for structural application; case hardened steel: for high tensile, torque and shear strength; and Climatek™ Coated: AC257 approved for use in treated lumber. They are intended for interior/exterior use in: carrying beams, ledger boards, stair rails, deck posts, playground equipment and other professional applications.