So we're setting hangers in an old building that had a clay tile ceiling that required 3/8" toggles 6" long for band iron hangers. We got this guy that was a sign guy just got into ventilation. I explained the MO I'm watching ,he's going a long I'm putting duct work together. At a point you transition to a concrete ceiling. It required a 3/4" 6" hammer drill bit for Hilti for toggles. Concrete you change to a 9/16" bit and a 3/8" drop in anchor that you use a setting tool to smack the bullet that swedges open the shell. I hear the different sound of the hammer drill and sure as $hit he's drilling a 3/4" hole in the concrete I stopped him at the 2" depth. WTF