I was going to hang a heavy whiteboard on my plaster walls using molly bolts, but when I went to drill the holes, the drill bit never broke through - it penetrated (exactly) 2" into the wall before hitting something hard and stopping. So molly bolts and wing anchors are out. Is there anything that will work in this case?
I estimate that the whiteboard weighs about 60 pounds, and it has 6 mount points.