Padded handle with split collar to slide over hollowing bar. This is referred to as a "side handle".
See "end handle " for the version of the handle that mounts in the end of the hollowing bar or extension. The current version of the hollowing bars and extensions are drilled and fitted with setscrews to accept the extension or handle. Now any hollowing bar can accept an extension or end handle. Earlier versions were not drilled and fitted with the set screws so if an extension or handle is desired, the bar will have to be machined.