Where in the body would you find a hammer?
I dont know if you're referring to the hammer as in the ear.
Also called the malleus.
"The middle ear, an air-filled cavity behind the ear drum
(tympanic membrane), includes the three ear bones or ossicles: the
malleus (or hammer), incus (or anvil), and stapes (or
stirrup)."
http://en.wikipedia.org/wiki/Ear