I drilled 2 large holes for mounting a flat screen in the bedroom. One hole is in a wood stud and the other is a metal stud. I will be renting out our apartment and will be taking the TV down and filling the holes and repainting walls. If I ever plan to move back into this apartment and mount a TV again in the same spot, how do I avoid not drilling in the same exact spot? Basically, I don't want to hit a portion of the same hole and create an even larger hole, making it very unsafe to mount a TV. Is there a way to mark the spot so that I know to avoid it in the future?
Chip away the drywall over the hole and install a Stud Plate. These are designed to stop anyone from drilling into a wire that runs through a stud.
Patch the drywall. Next time, if you can't find the location, and accidentally drill in the same spot, you'll hit the stud plate.
Why not just measure the height of your bracket and keep note of it, then next time mount it a few inches higher or lower so you don't risk hitting the same spots?
I suppose you could also plot the X,Y co-ordinates from a corner of the wall and mark those spots to avoid when you move back.
Why not just leave the bolts (lag, I assume) in the holes, screwed in below the level of the wall; then patch the wall. You can find them with a magnet if you ever want to reuse them.