Walls and Ceilings - Trouble drilling hole in hard wall; help?

I'm trying to install a 'picture rail hanging system' and I need to drill holes in my wall about 1cm down from the ceiling.

After drilling in just 1cm, the drill hits something solid, no matter where across the wall I drill, it always hits solid after just under 1cm. Could be steel or some sort of heavy duty concrete. Either way, I've tried 6mm masonary drill bit as well as high quality steel drill bit of 6mm also, but nothing goes through.

Any ideas?

Thanks

i gather- you are drilling into a concrete wall?
if so.you need a 'hammer'drill-not a plain electric drill.

Yes it is plaster covered wall. I have hammer drill with quality bits; to no avail.

what is the plaster covering?-concrete? wood framing?

concrete breeze blocks I think. It's a 1974 UK appartment.

Have you looked on the tip of the bit to see if metal filings are magnetically stuck on the tip? It have to be either an igneous rock you are hitting, or steel - like rebar, or an electrical protective cover plate, or a 'rafter tie'.