Carriage and Timber bolts have no drive, and machine threads for use with a nut.
Carriage heads are large smooth and domed with no drive.
A corrosion resistant steel alloy. The most common stainless steel for general hardware use.
A low carbon steel for general use. Zinc plated for moderate corrosion resistance.
Bolts with a very large flat head and machine threads for use with a nut.