Definition
A machine screw with a cylindrical head that has a slightly rounded top and a flat bearing surface underneath. The head is taller than it is wide, and a slot or recess is cut into the top to accept a screwdriver.
Plain English
A screw with a tall, round-sided head that sits up on top of the surface rather than being countersunk into it. The bottom of the head sits flat against the part being held down.
Context Anchor
Seen in aircraft maintenance, parts manuals, and hardware descriptions when identifying the correct screw head shape for an installation.
Derivation
The name comes from 'fillister,' an old woodworking term for a rabbet or rectangular groove. The screw head's profile resembles that stepped, squared-off shape when viewed from the side.
Why Pilots Care
Pilots performing preflight inspections or owner-permitted maintenance need to recognize hardware types so the correct replacement screw is used. Substituting the wrong head style can compromise how a part seats or is secured.
Intuition Check
A fillister-head screw is not a flat-head screw. It does not taper down flush with the surface; its head stays raised above the part.
Example Sentence 1
The technician replaced the missing fillister-head screw on the instrument panel cover with one of the same size and material.
Example Sentence 2
Fillister-head screws were selected for the engine baffle because their low profile avoided interference with moving parts.