A broadfork is kind of like the potato fork, only it has two handles with a wide square bottom. thet have more and longer tines. To use you stomp it in, you can get on the bar with both feet and put some weight on it. Then you just tip the handles down. It loosens the ground, not dig it.
I made a couple this spring and I am thinking this will be the solution to my short carrot problem. Rototillers make a hardpan 5 or 6" deep. I could feel it as I broadforked a chunk of my rototilled garden. The fork loosened the dirt a good deal deeper.
Outrageous that they are charging a couple hundred bucks for them though, they are easy to make.