Imperial CSK Slot Screws

Counter sunk Head: This has a flat top and a tapered underside that is intended to be driven into a countersunk hole.

Slotted: Slotted screw heads are perhaps the oldest and most common variety; a linear slot in the head accepts a standard screwdriver, which is also called a flat-head screwdriver

Machine screws have finer threads than wood screws. They are designed to be used in conjunction with a nut or tapped hole.