When a Phillips is not a Phillips Plus So Much More!

Step 18 Clutch Head Slot Security Screws

Clutch Head Security Screws are also known as 'One Way Screws' and are used for permanent installations. They can be installed using an ordinary screwdriver. The head of the screw has a normal drive face and a chamfered rear face which prevents the screwdriver applying torque when trying to undo the screws. Once installed these screws will typically have to be drilled out to remove them, however there is a special remover bit for these, as shown.

This unique feature renders the Clutch Head Screw tamper proof, reducing the risk of vandals or intruders tampering or undoing the screws. Due to the design of the Clutch Head Security Screw it is suitable for higher torque applications. From fellow instructable member lordzion: These screws are also referred to as Jail Head. Use is declining but they are usually self tappers, woodscrews or machine screws in applications of domestic window locks, Jail Cell hinges and exposed door lock screws.

Comments

[Dodgy]

OK, this isn't a perfect image, but it's close, I think. Perhaps someone can do better.

[Dodgy]

Some versions of these screw heads have a flat spot on the perimeter. This is presumably so a special tool can easily grip this, for removal. Defeats the purpose, I say! To undo it, you'd just need a ViceGrips with a round bit ground into one of the jaws.
Also, your B&W image isn't quite right. The white bits indicate where no metal is. But this screw head doesn't have 2 semicircular areas. It has 2 ramps and should (IMO) be indicated by gray bits. But you say gray bits are where special attention is needed, not necessarily intermediate height bits. I'll make an image...