Bellhanger’s Extension Drills are designed for drilling holes through masonry, concrete block, etc... so wiring can be threaded through these holes for cable TV, telephone lines, alarm systems, computer networks, and other electrical installations. Drills have a hole in the flute, sometimes called a fish eye, for connecting wire to the drill and then used to pull or fish wire, cable, or pipe through the wall. These drills are also known as Bellhanger Drill Bits, Installer Bits, Feeler Bits, Fishing Bits, Skylight Drills, Spotlight Drills, Installer’s Feeler Bits or Wire Installing Drill Bits.