Answer:
Iron on a mammal. Mammal on your feet.
I sleep by day, I fly by night. I have no feathers to aid my flight.
Hands she has but does not hold. Teeth she has but does not bite. Feet she has but they are cold. Eyes she has but without sight.
I turn around once. What is out will not get in. I turn around again. What is in will not get out.
If you break me, I do not stop working. If you touch me, I may be snared. If you lose me, nothing will matter.
Of these things - I have two. One for me - and one for you. And when you ask about the price, I simply smile and nod twice.