It's a french instrument called "Pince à Gigot". Sorry, i'm french so, it's a little hard for me to explain : you put it one the bone of a lamb or other animal leg in order to cut it more easily.
but i think a picture will explain it better :

http://www.parole-de-chef.com/wp-content/uploads/2007/03/maintenir-le-gigot-avec-la.jpg