business end of something
the business end (of something)
The functional part of an instrument, tool, or other object. These kids are reckless on the ice, so watch that you don't get hit with the business end of a hockey stick. My dad swung at the intruding squirrel with the business end of a broom.
business end (of something)
n. the dangerous end of something; the part of something that does something as opposed to the part one holds on to. Harry burned himself on the business end of a soldering iron.