🔍 Key Concepts

• An Allen head uses a recessed hexagonal socket driven by an Allen wrench (hex key), not a slot or external hex head • A set screw typically has no external head; it is usually fully threaded and designed to sit below or flush with the surface • Distinguish between screws that are driven by a slot vs those driven by an internal hex socket

💭 Think About

• Look closely at each listed figure and ask: which one is driven with a hex key inserted into the screw rather than with a screwdriver or wrench? • Which option shows a screw that is fully threaded with no distinct external head shape, meant to sit down inside a part instead of clamping with a head? • Can you eliminate figures that clearly show a slotted head or an external hex head that would be turned by a wrench?

✅ Before You Answer

• Verify that the figure you choose has an internal hexagonal recess in the top, not a straight slot • Confirm the screw appears to be a headless, fully threaded set screw, not a bolt or cap screw with a pronounced head • Double‑check that the remaining figures you ruled out either have a slot or an external hex head, which would not be an Allen head set screw