Flange bolts have a circular flange under the head that acts like a washer to distribute the load. Flange bolts that are non-serrated are sometimes called frame bolts.

Flange bolts, Hex flange, Zinc plated grade 8 steel, 5/8" x 1-1/2"

Non-serrated full thread grade 8 hex flange bolts

Full thread

A hexagonal head for use with a wrench. These bolts are sometimes called Frame bolts. Meets IFI-111 (2002).

See also

Flange bolts

Metric flange bolts

Flange bolts have a flange on the bottom of the head that distributes the load like a washer.