does anyone know how to remove this box section?

what is all that square section for?
thanks all

Dewalt makes a nice rivet gun, with a swivel head. It makes working in tight quarters a little easier.

Jerry

HomeDepot has all you need with this.

It's also reasonable to reassemble using machine screws and nuts rather than pop rivets if you prefer to do that. Getting wrench on the nut may be a bit tricky for some of them. (You probably could also get away with sheet metal screws in this case, being careful not to have them near anything that oughtn't get stabbed by their pointy end.)

You can pick up a pop rivet tool at most big box and hardware stores. They're easy to use.
https://www.google.com/search?source=hp&ei=11nsXPv8K4HcswXv3IyABA&q=pop+rivet+tool&oq=pop+rivet&gs_l=psy-ab.1.3.0l10.2402.4606..12727...0.0..0.214.1122.0j8j1....2..0....1..gws-wiz.....0.82RlQHbJpzI

is a pop rivet 'gun' available at hardware stores?
thanks

Drill out the center of the pop rivits with a 1/8" drill bit, then insert new pop rivits when you're through.