Plug followers are necessary for disabling and reassembling locks to re-key. Commercially produced plug followers can be purchased, though they are quite easy to make from wooden dowel. The purpose of the plug follower is to replace the plug when it is removed from the lock, trapping all the driver pins and springs in the bible. This allows you to remove the plug and key pins without removing the driver pins and springs as well. It also allows you to load springs and driver pins easily in preparation of reinstalling the plug. They come in a variety of sizes to replicate the common dimensions of plugs, though for many common North American brands, a ½ inch diameter wooden dowel cut to a 4 inch length will work nicely. A rectangular groove cut in the end of the dowel about ¼ inch deep will accommodate the shape of the rear of many common plugs and allow for easy installation of driver pins.
The Open Locksport Guide