O.K.  So that title could mean a lot of things.  When doing electrical work, one of the problems you frequently encounter is that of not knowing what is on the other end of the drill bit.  In my time I have bored holes through electrical wiring, sheet metal, ducting, water pipe, gas lines, and sewer lines.  (The last two instances were not aromatically pleasing.)

On one job I was drilling a hole through the floor of a mobile home and went through the top and bottom of a heat duct.  Electricians are not allowed to run wire through a duct, not to speak of doing so through an opening with sharp edges.

Certain places do not allow going through concrete.  In one instance I was drilling under a raised floor in the Davenport Hotel.  I was using a flat spade bit.  I pushed and pushed but it wouldn’t go through.  I noticed little copper shavings coming out of the hole.  I got my flashlight and peered into the hole.  There was a copper pipe with a pin sized hole where the tip of the drill bit had penetrated.  Around that pin hole the pipe was shiny where the spade bit had been chewing on it.

I checked to see where the pipe was going and to see if it was in use.  (No, I did not test for escaping gases using a match or lighter.)  We could not locate any information about the piping.  Nothing was escaping from the small hole, so we abandoned the pipe and relocated the drilling location.

One time I penetrated a PVC pipe while drilling.  In that instance I was able to reach the hole with some duct seal and close it up.

Another time we were working on a home that had been constructed by putting several cabins together.  We could not get through from one of the rooms to the room on the other side of the wall.  Upon further investigation we found a 10” gap between the rooms, caused by putting the different buildings together.  Of course it required a much longer drill bit to get through both walls.

Distance drilling also requires that the drill be perfectly perpendicular throughout the drilling process.  This is evident in situations with a large gap, or a thick beam.  If you don’t hold the drill precisely, the bit will exit in the wrong place and, probably, in a place that isn’t conducive to a good looking final trim.