Nooooo never heard such a thing re listen to that

Nooooo never heard such a thing re listen to that im positive its concrete thats the whole idea of a vault being no one can break through it ... Reinforced concrete lots of rebar in the wall slabs to prevent from break in... Along with a steelll DOOR which is very heavy.. That may be what u misinterpreted the vault door is made of heavy steel... The vault itself is prefabricated concrete vault system