I know this a irrigation forum. But I installed some landscape lights in some concrete this week. 7 lights that are in the concrete. This is a exsiting building. I'm goina give this a try. The building is on a slab with a hang over (like a side walk) so I had to core drill 7 -6" holes for the lights. Well 3 of the holes didn't have easy access to run the wire. So here is what I did. These three lights were on like a sidewalk that was against the building and the paved parking lot. So I drilled the holes, then I took 25' of 3/8 thread rod connected that to my 18volt drill. Then proceeded to run the rod under the concrete slab and try to hit my last hole that is 23' away. The first hole was perfect the 2nd was ok and the 3rd was ok as well. By this time I'm stoked that it even worked. Now for the hard part getting the wire back through the hole I just drilled. I connected the twine to the rod using the holeI drilled in the end for that purpose then, used the small twine then pulled my wire later with the twine. I can't believe it worked out as good as it did. It took 7hrs to do just the 3 lights.