As anyone installing wiring through walls knows firsthand that the tricky part is in maintaining continuity and in threading. That’s where these long special-purpose twist drill bits save the day. The secret is in their unusual length and the small hole in the solid shaft near the end. Drill the path for the wiring through multiple enclosed surfaces (for example, between adjacent rooms, studs or joists), then thread the wiring you are installing (electricity, ethernet, audio systems, coaxial cable, electronic devices etc) through the hole in the end of the drill bit and draw it back to you through all the holes at once. Presto. The wire is threaded and you know you have continuity. The set of five are all 24" long and range in size from 1/4 to 5/8 in diameter. Hugely useful when the situation calls.