Flat head types have flat surfaces that taper toward the screw body to allow for countersinking. The flat head lies flush against the workpiece.
Square drive types, also known as Robertson™ s drives, have square recesses and are driven with square drivers. They provide added torque when needed.
Steel is strong and durable but less corrosion resistant than stainless steel. To improve its resistance to corrosion, it may receive additional finishes and coatings.
