A slave pin is a pin used to hold a sub-assembly together/aligned while installing it into a parent assembly or housing.

For example, the trigger, trigger spring, disconnector, and disconnector spring all must be in the proper placement inside the lower receiver of an AR-15 before the trigger pin can be pushed through the holes on the trigger spring, trigger, and disconnector (all which must be aligned at the time). A slave pin is a shorter version of the trigger pin that fits inside the receiver while holding everything in the correct alignment. The trigger pin pushes the slave pin out of the way as it is inserted.

The following are the dimensions of some commonly used slave pins:

• • • AR-15 platform: trigger/disconnector slave pin is .154″ in diameter and .640″ long
    • Ruger 10/22: trigger/sear slave pin is 1/8″ in diameter and 1/2″ long

Slightly chamfer the edges of the pins. This will aid them in passing through holes that might not be perfectly aligned.