Last night I was try to put up a shelf across this narrow wall protrusion in my semi-finished garage. Magnetic stud finder registered on the edges but not in the center of the wall, so I believed it was a standard wood framed in piece of drywall. When I started drilling pilot holes I made it about 1/16" into the plaster before I hit something metal. Same on the other side. What could this be? It's garage level. I can't think of any reason why there would be a ventilation duct there, or why someone would skim coat a duct anyway.
- what could this be?
- can I still into it for my shelves, which I already cut to exactly the width of this wall?