A screw is a machine that transforms rotational motion to linear motion. When you turn a wood screw, for instance, you are adding torque, or rotational force, but the screw translates this to a forward force, pulling the screw into the wood. An Archimedes screw (known since at least the third century BC and attributed to the Greek mathematician) uses this concept to lift water. Here are two LEGO versions of Archimedes screws to move little balls up a slope, both by Akiyuky. BTW, these were built as modules in Great Ball Contraption layouts. The GBC is a collaborative LEGO project where people build different modules that move balls from point A to point B. These modules all get strung together to make huge mechanism that are fascinating to watch.