Hi there, I am trying to mount a 48" clothing rack on an interior plaster wall. On exterior walls, I have used 3/16 X 3 toggle bolts to mount heavy stuff including basically the exact same clothing rack and it was easy. When I drill into this interior wall to set up the hole for the toggle bolt, about 0.5 inches in I am hitting something extremely hard. I took out a 5/32 bit just to see if I could drill into it and after spinning the drill for 20-30 seconds I had made maybe a millimeter of indent in it. I tried my hammer drill with the same results. I'm stuck and not sure where to go from here. What is the substance behind the plaster and what's the best way to mount something heavy in it (~100 lbs)?

Is a phillips head screw driver ever referred to as a 3 point in the US? I am arguning with a Canadian. I have never heard the term 3 point when reffering to a philips in the US.