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
the part or end of something that actually does the work or carries out the procedure. Keep away from the business end of the electric drill so you won't get hurt. Don't point the business end of that gun at anyone. It might go off.