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.
Timber bolts have an oversized head to eliminate the need for a washer, and fins to resist spinning during installation.
Plow bolts are used for attaching the cutting edge of a plow to the plow blade. Flat head.
Bolts with a very large flat head and machine threads for use with a nut.