When pushers and ploughs are used, the belt's laterally stiff design guarantees that it will lie flat and continue to run in a straight line reliably. The lateral loading and discharge of goods is achieved by using very smooth, wear-resistant surfaces. Lateral sorters (e.g. carrier cells), on the other hand, require very thin, flexible belts whose surfaces have high coefficients of friction. Their special tension member construction means that they have very low energy consumption.