Box spanner is a familiar term used in mechanical engineering and construction for a specialized tool used to tighten or loosen bolts or nuts in narrow spaces. There are a variety of synonyms for box spanner, including the 'box-end wrench', 'ring spanner', 'flare nut spanner', or 'tube spanner'. Users can choose the most suitable spanner according to the job requirement and the space available to work. A box spanner offers excellent grip and doesn't slip off the nut/bolt during tightening or loosening, which makes it a handy tool to have in any toolbox. These synonyms highlight the various types of box spanners available, allowing users to determine the best tool for their specific needs.