Cable guide

Black plastic cable guide on the bottom of a Trek 5000 bottom bracket shell
Metal, braze-on cable guide on the top of a bottom bracket shell

A cable guide is a fitting or part of a bicycle frame which guides a piece of bare inner bowden cable around a corner. Most multi-speed bicycles have cable guides to get the derailleur cables past the bottom bracket. Older derailleur bicycles used either brazed-on or clamp-on guides just above the bottom bracket, but newer bicycles have a guide under the bottom bracket.