Hope I didn't throw you off with that heading.
The computer case is also called the chassis by some and I just wanted to put that out so you would know what others were talking about who prefer to use the term chassis.
I usually use the term computer case or just case but the term chassis is becoming more and more popular today. (I'm old school) To me this is the touchiest and most delicate part of the assembly.
That's because this is where you will be placing the motherboard very carefully onto the offset pins that's screwed into the computer case.