Head Styles Definitions - See Illustration Below 

• Binding - undercut unless otherwise specified -not recommended for phillips recess
• Fillister - deep slot used for counter bored holes
• Flat Fillister - same as standard fillister without oval top
• Flat 82 degree - used where flush surface is desired
• Flat 100 degree - larger head than 82 degree used for thin metal soft plastic
• Flat Trim - same as 82 degree except diameter and countersink depth reduced
• Flat Undercut - standard 82 degree with lower 1/3 countersink removed for short screws
• Hexagon - manufactured as trim hex or indented hex
• Hex Washer - same as hexagon with washer section
• Oval - same as flat head with rounded surface for appearance
• Oval Undercut - similar to flat undercut with rounded surface
• Oval Trim - same as oval - smaller diameter and countersink
• Pan - recommended to replace round, truss binder
• Round - general purpose (see pan head)
• Round Countersunk - bolts only - similar to flat head with no driving recess
• Round Washer - same as round head with integral washer for bearing surface.
• Square Bolts - large bearing surface for wrench tightening
• Square Countersunk - for use on  plow bolts
• Square w/Set Screw - recommended for high torque assembly
• Truss - similar to round head with larger diameter (see pan head)