Are You Smarter Than a Kindergartener?

On Friday, Jack brought home some worksheets to do that he had missed while absent from school. I was looking over one of the worksheets, and just could not figure out this picture.

(please excuse the poor picture quality)

I stood there for a solid minute and all I could come up with was 'ham hock'. I showed it to Brent and he had no idea what the picture was either! Now we have 15 years of post graduate education between us, how can we be stumped by this?!?!? Jack comes over to see what is so interesting and glances at it for half a second and says "Flat tire...easy."

We were howling!!