A cart includes a platform assembly, a handle assembly, first wheel assembly and a second wheel assembly. A wrapping device 1 covers a top opening of a tray T with a stretch film Fm, welds the stretch film to the tray T, and thermally cuts it. These sensors measure instantaneous changes in acceleration in xyz axis and changes in earth magnetic field\u2014relative to the skier position, to provide six degree of freedom in calculation of skier position as well as moments applied to the ski edge and forces experiences by the skier body. Control systems may also monitor the position of a wafer feature as it rotates, such as a notch in the edge of the wafer.