bob wrote:
I need some ethernet cables between my computer room and the TV room.
The easiest way is to run the cable in the crawlspace and then up
through the floor for about 1 foot.

The plan is to drill a hole from the crawlspace up into the space
between two inside walls (one of them is the TV room) and between two
studs. Then I can make an opening on the wall for the faceplate and
the network jack. There is an electrical outlet on that wall, but I
don't think that's going to help.

If I could drill the hole from the top between the walls and between
studs, that would be easy. But since I can't get a drill inside the
walls, I have to drill up from the crawlspace. How do you identy the
area between two drywall, from the crawlspace looking up?

This may work:

Assuming you can find the wall, drill away. You've got an 90% chance of not
hitting a stud. If you do drill six inches or so, with plenty more to go,
stop and move over three inches.