I live in an apartment in NYC, built in 1973. I'm trying to mount something to the wall which requires two screws placed 5 inches apart vertically.
I used a stud finder to find a vertical stud in the wall (3 inches across), but when I drilled it went in an inch before encountering a hard surface. Definitely not wood. I applied pressure and drilled, and it finally "broke through" in a matter of seconds, and it felt like there was nothing behind that.
I tried screwing in a screw, and it gets to the 1 inch point before making a metallic grinding noise -- I'm assuming what I drilled through was some sort of metal plate. The screw definitely "threads" (if screwed in, it cannot be screwed out), but it's very loose and unable to be tightened.
So, what is this vertical thing behind my drywall? How can I mount things to it?