Plug follower

A plug follower is a locksmithing tool used in the rekeying of pin-tumbler locks. They are made of metal, wood, or plastic and have a cylindrical shape.

Principles of operation
The diameter of most plug followers is 0.395 to 0.500 inches, but can vary depending on the brand of lock cylinder the follower is being used with. The plug follower slides into a cylinder housing at the same time the plug is being removed. This prevents the driver pins and springs from falling out of the cylinder housing and speeds up the rekeying process.

Core shim
Very thin, curved strip of metal -- typically .0015 inces thick -- that is inserted between the plug and cylinder housing from the rear of the lock. Shims prevent driver pins and springs from falling into cuts in the plug while the core is being removed. They can also be used from the rear of the lock to hold pins at the shear line during lockpicking.

Pinning shoe
A tool inserted from the front of the lock to retain driver pins and springs in the cylinder housing while the plug is removed. It is used in combination with a slotted plug follower that allows the shoe to remain in place while the follower is inserted. Pinning shoes are typically used to disassemble euro profile cylinders.