floor connected to shell?

I asked about a rear bath and was told about potential sag, and i was talking to my 14 year old and he said how is the floor connected to the shell, and i had to say, "I don't know, but let me ask the experts."

So, how is the floor connected to the shell? is it riveted? the aluminum shell to the steel bottom frame? and also, could you tell me how to say these things correctly? :-)



Thank you.



Lisa