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.
Grade 5 falls between grade 2 and grade 8 in strength, and is commonly found in automotive applications. 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.