A general purpose screw typically used in exterior wood to wood projects. A countersunk flat head that is concave under the head. Distributes weight over a wider area. Square drive is designed to reduce the risk of cam-out (stripping) and allow single-handed installation.
The most common stainless steel for general hardware use.
A highly corrosion resistant grade of stainless steel. Ideal in salt water and chlorine environments. More expensive than 18-8.