wiring
I am looking to fish some Cat 6 network cables from the basement to the attic.
Initially, I was going to attempt using my bedroom's cold air return vent, but it appears that it's not a straight shot to the basement. There is a 90 degree turn somewhere, and I don't know how to use my 100ft. fish tool (or any other type of tool, for that matter) through it.
That is what I'm referring to the cold air return vent:
How can I achieve this before I find another solution?
Consider through the crown molding, or installing some to hide the dable. See my response to wiring rear speakers
Couple problems I see. First is the textured ceiling. You'll never be able to open that up and patch it without being obvious, the texture is something that just isn't done these days. Second, the exterior wall should have insulation in it, so you'll end up fishing the line through insulation and the vapor barrier.
Instead, I'd suggest running the line around the floor if you can get it to a convenient wall anywhere in that room. Use some fasteners to keep the cable at the base of the wall to run it around the room:
Best Answer
Your "intake vent" is better referred to as a "return air vent in the stud wall cavity". The reason there appears to be a 90 degree turn in it is because there is! Behind the drywall, at the base of the wall, there is a hole where the floor would be, this transitions into a metal duct which travels back to your HVAC unit, just like you see if you open up your floor registers; the air is just moving the other direction.
I would not drill a hole for your Cat6 cable in the attic OR the basement in this stud cavity for this reason. Rather, pick an interior wall stud cavity where you have basement access (try the utility room) and there aren't preexisting electrical runs. Drill a hole from the attic and basement (alignment doesn't need to be perfect, just hit the same cavity). Use a paperclip & string from the top, and magnet from the bottom, to fish a line between the two. Then use that line to pull your Cat6 cable through.