I've used them sparingly. Once I was drilling down from the attic (10' ceilings in the living room) through the top plate with ease. Then came the fire break, like you've heared, drilling blind. I drill into a hot romex conductor. Ya you guessed it, after the sparks and #$@% stopped flying. I choose what I feel is a very useful help, drill a second hole next to your first hole in the top plate and use it as a portal for you to spot your bit in the center of the fire break ensuring that your not drilling a hot condutor.
Good luck, Bert
