You should have a housing on your car already. If you don't you might notice a rapid drip of coolant.
New naked thermostats (w/o housing) come with a cardboard "tampon applicator" tube, you just have to push the ears of the stat and twist. You can also use a 19mm ish socket.
New naked thermostats (w/o housing) come with a cardboard "tampon applicator" tube, you just have to push the ears of the stat and twist. You can also use a 19mm ish socket.