What are security pins?

Security pins are components used inside pin tumbler cylinders to make locks harder to pick. They come in two main types: serrated pins and spool pins. Serrated pins have ridges cut into their sides, while spool pins are mushroom-shaped with a wider top section that narrows at the waist.

When a picker manipulates a lock with standard pins, they can feel when each pin sets at the shear line (the boundary between the plug and bible of the cylinder). Security pins work by binding at multiple false points as they move upward, creating the sensation that the lock is opening when it actually is not. A spool pin, for example, can catch and bind on the edge of the bible before reaching true shear, giving the picker incorrect feedback about when they have found the correct height for each pin.

This feedback creates picking resistance because an attacker must distinguish between real and false binding points through feel alone, making manipulation significantly slower and more difficult. Different pin designs create different levels of feedback, so locks combining multiple security pin types (spools with serrated drivers, for instance) are harder to defeat than those with just one type.

Locksmiths and lock manufacturers in Singapore use security pins to upgrade residential and commercial cylinders when clients need protection beyond basic pin tumbler locks. Understanding these pins is essential for locksmiths servicing residential clients who want improved security without replacing entire lock mechanisms.