Then we made a ball and socket joint, but I was not satisfied that they could understand how the ball and socket joint worked by just looking at a flat model, so I dug out a Zoob and showed how they snapped together in the same way. Steven then found a model of this joint that I had made for Katie years ago using a ping pong ball and a cylinder made of paper. They could put the ball in their cupped hands and see how the ball and socket joint works.
We talked about the strengths and weaknesses of each joint (the flexibility of the ball and socket joint, the strength of the hinge joint...etc.) and they located each of the joints in their own body.
These models can be found in The Body Book by Donald Silver and Patricia Wynne.