Screw Heads and Drive Types

Head Styles
	Bugle	Similar to a flat head, however these have a more curved neck that sinks into drywall without tearing its paper surface.
	Fillister	Designed to maximize driving power by combining the greatest head height with the smallest head diameter you can get in a machine screw.
	Flat	Angled under the head to provide a flush surface when countersunk in a hole
	Hex	Have 6 flat sides for tightening with a wrench.
	Hex Washer	Have 6 flat sides for tightening with a wrench and a washer face to provide a larger bearing surface.
	Modified Truss/K-Lath	A one-piece washer and round head combination that provides a large/low profile bearing surface.
	Oval	Similar to a flat head, these are angled under the head so they can be countersunk in a hole. However when installed, the rounded top sits above the surface providing a more finished appearance.
	Pan	General purpose screws with moderate head height and head diameter.
	Round	Similar to pan head, round head screws have a thicker decorative round head that provides a more finished appearance.
	Truss	A larger rounded head that is wider than other head styles for a strong hold in thin materials.

Fastener Technical Guide