When a Phillips is not a Phillips!

Ever wondered why there are so many different types of screws?

Each screw type tries to solve a certain type of engineering problem; for example the star screw (commonly called phillips screw) is made so that one cannot over tighten the screw (this is based on the principle of cam-out, where when excess torque is applied the screw driver pops out of the screw). Intrigued? Instructables has an excellent post that describes 28 different types of screws and their disadvantages and advantages.

When a Phillips is not a Phillips! - More DIY How To Projects

An interesting screw type is the modified phillips tamer-proof screw, which uses a pin in the middle of the screw, to make it impossible to unscrew the screw, unless one has a matching screw driver with a hole to match the pin the screw’s head.