pickstock, I think the Pellpress link at the top of the page might show you. If not, a wee bit of Googling will get you there. Basically the material to be pressed is in a circular container and rollers push it through a plate with holes drilled in the plate so as to form "rods" of material. The system used (minus the holes) is extremely ancient and still used in my neck of the wood for crushing olives, including the stone, for the making of olive oil.