On Tuesday, December 17, 2002 at 11:34:57 AM UTC-5, DBM wrote:
Thank you very much for your suggestions. Let me try to summarize
your questions so far:

1. Is it a newer home? Yes, it's 5 years old.
2. Are there metal studs? I doubt it. The attic studs are all wood,
but I can't be 100% sure since this is between the first and second
floor.
3. Is it a nail guard? That's what I thought, but can it be that I
can be so lucky that I managed to find nail guards at four different
random locations? Is there ever a case when the nail guard extends
the length of the whole beam?
4. I would be afraid to drill blindly through it just in case there
is some electrical wiring or piping.

Any other thoughts?

Thanks!
Doug

Did you figure out what this was? I'm having a similar issue with my garage ceiling.