The prepress flaps in the filling opening of the press close simultaneously, resulting in a closed press channel. Because of this, optimal-weight homogeneous bales are produced without cutting being necessary. These flaps have been constructed in such a way that any impacting forces are effectively absorbed. The front flap is smaller in view of the distribution of forces, and is equipped with a knife so that material between the flaps can be cut. The rear flap is equipped with a fallback mechanism and anti-blockage switch, which minimizes interventions. Because of this, materials that are difficult to press can be processed as well.