what are the metal hoops latches in the rear hatch?

They can be used with the cargo mesh as hold down points, I think. Also, if you've swapped a flat tire for the temp spare, there's a hold-down strap for the flat that loops through those rings. I think. Look in the flat tire section of the manual to verify, I'm a little fuzzy on that.

 

Cargo hooks. (see p. 333 of the destruction manual (for 2009 Gen II)). I bought a very nice cargo net from Ye Olde PriusChatte Shoppe (thanks Danny!) Spider Cargo Net for 2004-2009 Toyota Prius - OEM - PriusChat Shop

 

Destruction Manual..., my father-in-law was always talking about those.

 

I use them for tying down the grandchildren when they start getting too noisy.

 

I had a wall full of them at work - they were officially called something like "Official Government Policy & Procedures" - but destruction manuals to all who knew and hated them.

 

Yep, those hooks are for cargo net. There are two on the side and two at the bottom.

 

Yes, for cargo net, or I use them for cargo elastic cord hooks (or whatever they are called in English I don't even know the name in Italian (I am italian, but live in Germany)....
With the cords, I keep a small crate full of the things I need to carry around or avoid small objects I might buy in the supermarket, start moving around. Actually it is better now than in Gen3, as I had the crate folded back in the underfloor compartment - this way I was forced to take it out and actually use it, and it is really cool to have it there open, ready for use.