These are wood screws with a flat top with a countersunk bearing surface, Original Robertson® square drive, self counter-sinking Nibs, Lo-Root® Thread, and the Aster® Thread Feature. Lo-Root® Threading provides a single lead deep thread with a wide spacing for superior holding in softwoods and particle boards. Aster® Thread Feature is now standard on all Lo-Root® screws with a serrated tooth thread design, providing quicker starting, reduced splitting and less drive torque. Aster® serrated teeth on all Lo-Root Deep Threads provide greatest holding strength in soft woods and particle boards. Sharp thread angles and points offer excellent penetration and engagement. Self-countersinking nibs under the head. All Screws under 1" are fully threaded. Screws over 1" are 2/3 threaded to help prevent "jacking" when two materials are fastened together.