A RAY or BEAM is a straight line of light or energy that travels in a single direction. The term 'RAY' is often used to describe a BEAM of light, while the term 'BEAM' is used to describe a BEAM of energy, such as an X-RAY or gamma RAY. A SHAFT is a long, cylindrical object, usually made of metal, wood, or plastic, that is used to transmit power or motion. In the context of a crossword puzzle, a SHAFT could refer to a BEAM of light or energy, or it could refer to a physical object.