Phillips recess provides smooth engagement with moderate torque transmission. Bugle head provides consistent penetration without damaging the paper. Coarse threads are ideal for use in wood connections. Ultra sharp point quickly penetrates wood reducing drive time. Gray phosphate is an economical rust inhibitor meant for interior applications only. Exterior finish exceeds 1000 hours salt spray per ASTM B117. Use a screwdriver with a precise depth-sensitive clutch and speeds of up to 5000 RPM. Overdriving may cause a weak connection. The drive is finished when the screw is just below the work surface without tearing the paper. 1†of penetration is suggested for drywall to wood applications.