The ferrule is one of the most overlooked parts of a pool cue. However, a cue without a ferrule will soon be destroyed since the force of cueing a shot will eventually split the shaft closest to the tip. To forestall this, the end of the shaft is machined (while on a lathe) to reduce its diameter, and a hollow plastic (or plastic-impregnated fiberglass) ferrule is slipped on and secured with glue. Then, both the shaft and the newly-installed ferrule are returned to the lathe and sanded to bring them to the same diameter.
Different cue-makers prefer different styles of ferrule. Some, like Meucci, prefer a long, thin-walled ferrule. Others, like Joss, install shorter, thicker ferrules. In general, a thinner ferrule is preferable, since the glues typically used to install cue tips don't adhere as well to the non-porous ferrule as they do to the wood of the shaft.