>>>bar - rebar (what's rebar?)
>>
>>I think it's something American... some sort of iron bar. Don't know exactly what.
>>
>
>Rebar is used inside cement during construction. You've probably seen the stuff when you walk by a construction site.

Ah, that's what we called "armatura". I've placed a bunch of it in my house back home - the 12mm goes for the corner pillars, above the doors/windows and the circlage, 6 or 8mm goes for most of the other stuff, 6mm grid goes into the floating cement board on the floor (had to float on a layer of insulation, because it contained the warm water pipes for in-floor heating).