Actually, I was wrong about that. Turns out the floor/ceiling was 21" (53 cm) thick. The hole is now in place. It turns out that a 5/8" hole is just right for an RJ45 connector, but only because Victor's 21.5" long drill bit (yes, we just made it!) was so out of true that the hole is probably closer to 3/4" than it is 5/8".

Now, next question in a row.

Have any of you ever taken apart a WRT54GL router? It would simplify my installation somewhat if I could drill through the mounting feet of the router and just run the screws directly into the ceiling, but I don't want to go stirring up bits of electronics with my drill bit. The mounting feet are indented at the top and project out the bottom, so that multiple routers can be stacked on on top of another, but are not hollow all the way through.

What are the chances that I could fun a 1/8" or 3/16" drill bit through them?

tanstaafl.